Combine tomatoes, onion, cilantro, lime juice, serrano pepper, garlic, 1-1/2 teaspoons olive oil, chile powder, salt, cumin seeds and black pepper, to taste in large bowl; mix well.Pat corn kernels dry with paper towels.
Heat dry corn in medium nonstick skillet over medium-high heat 2 to 3 minutes or until toasted.Stir into tomato mixture; mix well. Cover; refrigerate at least 2 hours to allow flavors to blend.
Heat 1 tablespoon oil in medium skillet over medium-high heat. Add turkey; cook and stir 4 to 5 minutes or until heated through. Season with additional chile powder to taste. Cover; keep warm.
Warm tortillas in separate skillet about 1 minute per side or until heated through. Fill each tortilla with lettuce, 1/4 cup turkey and 1/4 cup salsa. Serve with sour cream, if desired.
