For the soup, in a large saucepan or Dutch oven set over medium-high heat, heat 2 tablespoons of the olive oil. Add the onion and garlic. Cook, stirring frequently until translucent and fragrant, about 3 minutes. Add the tomatoes and their juice, chicken broth, pesto, and honey or sugar, if using. Bring the soup to a simmer and cook for 5 minutes.

Using an immersion blender, blend the soup until smooth. (Alternatively, puree the soup in batches in a standard blender.) Stir in the feta cheese and bring the soup just to a simmer and cook for 10 more minutes. Remove from the heat and stir in the Greek yogurt and season to taste with salt and pepper. 

To serve, pour the soup into individual bowls and garnish with additional feta if desired. The soup will keep in an airtight container in the refrigerator for up to 3 days.