- Heat grill to medium-high.
- Combine avocado, cilantro, sour cream, lemon juice, and garlic in bowl of a food processor. Process until smooth, adding a tablespoon of water as needed to make a thick sauce. Season with salt and pepper.
- Toss tomatoes with oil and season with salt and pepper. Transfer to grill and cook until softened and lightly charred, about 3 minutes per side.
- Transfer to serving plate and top with sauce, cilantro, and a drizzle of oil.