For salsa, brush tomato halves with 1 teaspoon of the olive oil; place on the unheated rack of a broiler pan. Broil 4 to 5 inches from the heat for 8 to 10 minutes or until tomatoes begin to char, turning once. Remove from broiler pan and cool slightly; coarsely chop.
Meanwhile, in a medium bowl combine the remaining 1 teaspoon olive oil, beans, green onions, cilantro, lime juice, serrano pepper, and salt. Stir in tomatoes and any juices. Set aside.
For waffles, prepare corn muffin mix according to package directions, except stir corn into batter. (If necessary, add 1 to 2 additional tablespoons milk to thin batter.)
Pour about half of the batter onto the grid of a preheated, lightly greased waffle baker. Close lid quickly; do not open until done. Bake according to manufacturers directions. When done, use a fork to lift waffle off grid; keep warm. Repeat with remaining batter.
To serve, cut waffles in half. Divide warm waffles among 4 serving plates. Dollop with salsa and yogurt. If desired, garnish with cilantro sprigs. Makes 4 servings.