I like our lentil soup with the veggies pretty blended in, which is why I chop them finely in a blender or food processor. You can also just chop them with a knife. (Recipe updated August 2020 to saute the veggies before simmering to ensure that there's no raw onion flavor.)
Add the onions, carrot, garlic, thyme, and salt to a blender or food processor. Grind to chop finely.
Heat olive oil in a medium pot over medium heat. And the vegetables, stir to coat, and cook for about 6 minutes or until just starting to soften.
Add the tomatoes and broth, cover, and bring to a boil.
Remove cover, reduce heat to a simmer, and stir in the bay leaf and lentils. Cover slightly, so the lid is just partly on and some steam can escape, and simmer until the lentils are soft or about 20-25 minutes
Serve topped with Parmesan cheese, if desired.
Store leftovers in the fridge in an airtight container for up to 3 days or in the freezer for up to 3 months. Thaw in the fridge overnight or use the defrost setting on your microwave, then warm through at regular heat once thawed. Stir in a little water when reheating if the soup has become very thick.
To make this without a food processor: Simply finely chop the veggies and proceed with the recipe.
You can also chop the veggies with a knife, then puree the finished soup for a smoother option.
Top with Parmesan cheese, shredded cheese, additional salt and pepper, and/or hot sauce for parents as desired.