Heat the olive oil in a 4 to 5 quart Dutch oven or soup pot over medium until shimmering.
Add the onions, celery, peppers, and leeks and saute until they begin to soften, 5-8 minutes.
Scootch the vegetables to one side of the pot and add the garlic, tomato paste, smoked paprika, and Italian herbs to the cleared side. Add a splash of broth and stir the paste and seasonings together until loose and fragrant, then mix into the rest of the vegetables.
Increase heat to medium-high and pour in the remaining the vegetable broth and fire roasted tomatoes. Bring the soup to a light boil
Add the summer squash, zucchini, potatoes, and cabbage to the pot and give everything a good stir. Adjust the heat to maintain an active simmer.
Cook the soup for about 20 minutes. Check the cabbage for doneness. I like a little bit of sturdiness to the leaves rather than a full, soft wilt. When the cabbage is done to your liking, remove the soup from the heat.
Stir in a tablespoon of the lemon juice, and give the soup a taste. Add salt, black pepper, and lemon juice as needed, until the soup is flavorful and pops with flavor.
Sprinkle the fresh parsley or cilantro over the soup before serving.
