Lightly spoon flour into a dry measuring cup; level with a knife. Combine flour and next 5 ingredients (flour through salt) in a large bowl. Make a well in center of mixture. Combine milk, oil, honey, and egg. Add to flour mixture, stirring just until moist. Fold in corn, onion, and jalapeño.
Place a cast-iron cornstick pan in a 425° oven for 5 minutes. Remove from oven; immediately coat with cooking spray. Spoon batter into pan. Bake at 425° for 18 minutes or until lightly browned. Remove from pan immediately; serve warm.