In a large pot, heat olive oil to medium-high. Cook and stir garlic, onions, and bell peppers until softened, about 5 minutes.
Add the tomatoes, vegetable broth, salt, and red pepper flakes and stir to combine. Once the mixture starts to boil, turn the heat down to low and simmer for 15 minutes.
Using a hand-held immersion blender, blend the soup until smooth.
Add milk and stir to combine.
Turn the heat up to medium, add the tortellini, and cook for 7-9 minutes, until tortellini is fully cooked.
Serve immediately.
Notes
I used frozen tortellini for this recipe, but you can also use refrigerated tortellini. Just decrease the tortellini cooking time by a minute or two.