Slow Cooker Tomato Basil Soup

Tomato soup is one of those recipes that is so good made in the slow cooker, and no messy bench tops to wipe up from splatters!

Unlike many tomato soup recipes, the tomatoes for this dish don’t need to be roasted first, which keeps the preparation simple while still producing a rich soup.

This version starts with a quick sauté of onion, garlic and red bell pepper before everything goes into the slow cooker. That first step builds the foundation of the soup, and from there the slow cooker quietly does the rest of the work.

If you enjoy slow cooker soups like this, my Slow Cooker Minestrone Soup is another cozy option with a tomato-based broth filled with vegetables and beans.

Why This Tomato Soup Doesn’t Need Roasting

The soup begins with sautéing onion, garlic and red bell pepper in olive oil. As the vegetables soften they become slightly sweet, which gives the soup its base.

Once the bell pepper begins to soften and the onion smells sweet and fragrant, tomato paste is added and cooked briefly adding more depth to the flavor. Then when you add the tomatoes I also use a puree passata or tomato pasta sauce – this combo brings that richness and body you get from roasting.

Over the next several hours the tomatoes soften and begin to collapse, releasing their juices into the soup.

If you’re new to slow cooking or want to understand how different cook times affect texture, this guide to Slow Cooker Cooking Times explains how Low and High settings work and when to use them.

How to Prepare Fresh Tomatoes for This Soup

The tomatoes don’t need to be peeled. Once the soup is blended the skins break down easily and almost disappear into the soup. Some texture from the skins remains but that gives it a homemade rustic vibe.

The tomatoes are deseeded before cooking. This removes excess liquid and hard core while keeping the flavorful tomato flesh.

After deseeding, the tomatoes reduce from about 2½ pounds (1.2 kg) to roughly 1¾ pounds (800 g) of usable tomato flesh which is the perfect amount.

Roma tomatoes work beautifully here because they’re naturally meaty, but vine-ripened, heirloom or even cherry tomatoes will work well too.

If fresh tomatoes are out of season or a little bland, good-quality canned whole tomatoes such as San Marzano can be substituted for deeper taste.

If you enjoy making homemade soups in the slow cooker, this guide on How to Make the Best Slow Cooker Soups shares a few simple techniques that help soups develop a deeper taste and better texture.

Why Basil and Cream Work So Well in Tomato Soup

A generous handful of basil gives the soup that classic bright hit. Because the soup is blended, the basil distributes evenly through the whole pot and is such a nice contrast.

A small splash of cream is also added at the same time. It doesn’t turn the soup into a heavy cream soup, but it softens the acidity of the tomatoes and gives the soup a smoother mouthfeel.

The Simple Trick That Brightens Tomato Soup

One of the easiest ways to improve tomato soup is to balance the flavors at the end.

After blending, taste the soup before adjusting anything. Tomatoes vary in sweetness and acidity, so sometimes only a small adjustment is needed.

A splash of apple cider vinegar or lemon juice brightens the tomato flavor and lifts the entire soup. It’s a small step but it makes a noticeable difference.

Once you start tasting soups at then end you learn that this is where the balance of salt, fat and acid comes into play. The cream provides richness, the seasoning brings out the natural sweetness of the tomatoes, and a little acidity sharpens everything so the soup tastes lively rather than flat.

If you enjoy a slightly deeper flavor, a small amount of balsamic vinegar stirred in at the end works beautifully as well.

Blending the Soup Until Smooth

An immersion blender works well directly in the slow cooker, but a heat-proof blender will give the smoothest texture.

After blending, the soup should look smooth and slightly glossy. Taste again and adjust the seasoning if needed. Often a small pinch of extra salt helps the tomatoes shine.

If you ever find a slow cooker soup or sauce a little thinner than you’d like, this guide on How to Thicken Slow Cooker Sauce shares a few easy ways to adjust the consistency.

How to Make Slow Cooker Tomato & Basil Soup

1. Sauté the vegetables
Heat the olive oil in a skillet. Cook the onion and bell pepper until starting to soften, then stir in the garlic and tomato paste and cook briefly until slightly darkened.

2. Transfer to the slow cooker
Add the sautéed mixture to the slow cooker along with the chopped tomatoes, seasonings, passata and vegetable broth. Stir to combine.

3. Slow cook
Cook on Low for 6–8 hours or High for 4 hours, until the tomatoes are very soft and beginning to collapse.

4. Add basil and blend
Stir in the fresh basil leaves and cream, then blend the soup until smooth using an immersion blender or heatproof blender.

5. Finish and season
Taste and add a splash of apple cider vinegar or lemon juice to brighten the soup. Adjust seasoning if needed and serve warm.

What to Serve with Tomato & Basil Soup

The ultimate combo is tomato soup & grilled cheese sandwiches. The crisp toasted bread and melted cheese are perfect for dipping into the smooth soup.

Crusty bread or warm dinner rolls also work well, and homemade croutons add a nice bit of texture.

A drizzle of pesto over the soup is another simple way to add extra flavor.

Storage and Reheating

Allow the soup to cool to room temperature before storing. It will keep in the refrigerator for up to 4 days.

The soup also freezes very well. Store in airtight containers or freezer bags for up to 3 months. Reheat gently on the stovetop or in the microwave until piping hot.

More Slow Cooker Soup Recipes

If you enjoy this tomato basil soup, here are a few more slow cooker soups to try:

• Slow Cooker Minestrone Soup
• Slow Cooker French Onion Soup
• Slow Cooker Ham & Vegetable Soup
• Slow Cooker Chicken Noodle Soup

I hope you love this soup!

I hope you love this tomato soup as much as we do. We make it over and over in the summer, perfect to gift to people who are under the weather also.

If you try it, I’d love to hear how it turned out for you in the comments below. 

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Thank you so much for visiting and taking the time to try this recipe. I hope you find plenty of slow cooker inspiration here on my blog.

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Happy cooking!

Anna