Combine milk, honey, and 1/4 teaspoon lemon rind in a small saucepan; cook over low heat until mixture reaches 110°F, stirring occasionally. Remove pan from heat, and add yeast; cover and steep 15 minutes or until yeast begins to foam. Whisk together cornmeal and milk mixture in a bowl until smooth. Cover and let rise in a warm place (85°), free from drafts, 30 minutes. While batter is rising, place blackberries in a bowl; sprinkle with 3 tablespoons sugar. Stir in lemon juice and remaining 3/4 teaspoon lemon rind; allow berries to sit at room temperature 30 minutes, stirring occasionally.
Beat egg whites at low speed with an electric mixer until foamy. With machine running on low, add remaining 2 tablespoons sugar, 1/2 tablespoon at a time. Increase speed to medium, and beat until medium-stiff peaks form. Once dough has risen and soaked up most of the liquid, fold one-third of beaten egg whites into dough batter. Add a second third of egg white mixture to batter, and fold until well incorporated. Fold in remaining egg whites, being careful not to overmix or deflate batter.
Heat 1 tablespoon butter in a cast-iron skillet over medium-high heat. Add batter, 2 rounded tablespoonfuls at a time, to form cakes about the size of silver dollars. Cook cakes 1 1/2 minutes on each side or until golden brown and cooked through. Transfer to a plate, and keep warm. Repeat with remaining butter and batter. Serve macerated blackberries and juices over cakes and ice cream.