In a large pot, heat the olive oil over medium heat. Add the onion and garlic and cook until tender, about 5 minutes. Stir in the bay leaves and crushed red pepper flakes.
Add the diced tomatoes and vegetable broth. Stir in fresh basil and season with salt and black pepper, to taste. Simmer on low for 15 minutes.
Remove the bay leaves from the pot. Use a hand immersion blender to blend the soup (or carefully transfer soup to a blender to blend and return to the pot). Stir in the Greek yogurt until well combined. Stir in the cheese tortellini and cook on medium-low until tortellini is cooked, about 7-8 minutes. Serve warm.