Heat olive oil in a large pot over medium/high heat. Wait until the oil is shimmering before adding the next ingredients. This step is crucial as it helps to sauté the vegetables evenly.
Add onion and garlic. Sauté until the onion becomes translucent and fragrant, about three to five minutes. Be careful not to let the garlic burn, as it can turn bitter.
Stir in red pepper flakes. This will infuse the oil with heat, enhancing the overall flavor profile of the soup.
Add in the chopped zucchini, yellow squash, and red pepper. Continue to cook for another five minutes until the vegetables start to soften.
Incorporate the chopped fresh tomatoes next. Stir them in and let them cook down slightly, about two to three minutes.
Stir in the diced tomatoes, vegetable broth, and water. Bring the mixture to a boil.
Add in the rosemary and let the soup simmer for about ten to fifteen minutes. This allows all the flavors to meld beautifully.
Stir in the cheese tortellini and spinach. Cook until the tortellini is tender and cooked through, which usually takes about five to seven minutes.
Season with salt and pepper to taste. Adjust the seasoning until the flavors are just right for you.
Enjoy! Serve your soup hot and savor all the wonderful flavors you've created.