Set a rack in the middle of the oven and preheat to 400 degrees F. Grease a 6 slot muffin pan with non-stick vegetable spray.
In a small saucepan, melt the butter. Add the onions and garlic and cook until soft.
In a large mixing bowl, whisk together the milk, eggs, bell pepper, jalapeno, corn and cilantro. Whisk in the butter mixture.
In a separate bowl, stir together the cornmeal, flour, baking powder, soda, salt and sugar. Mix into the liquid mixture.
Divide the batter evenly among the muffins slots and bake for 16 minutes or until set, turning the pan once for even baking.