Combine salsa and sour cream in a large bowl; cover and refrigerate until ready to use.
Heat oil in a large nonstick skillet over medium heat. Chop onion, mince garlic, and add to skillet; cook 2 minutes until softened.
Add turkey and cook 5 minutes more or until cooked through, stirring often to crumble.
Dice tomatoes and add to turkey; stir in rinsed and drained beans, cumin, and chili powder.
Continue to cook and stir 2-3 minutes until the tomatoes begin to break down. Remove from the heat, then stir in cilantro and 1/4 cup of the salsa mixture.
To serve, divide the lettuce among 4 plates, top with the turkey mixture and remaining salsa, and sprinkle with cheese.