5 tablespoons unsalted butter, melted and cooled, plus more for greasing
1 egg, lightly beaten
1 cup (4 ounces) grated Monterey Jack cheese
Set the oven to broil, with the rack about 6 inches away from the heat source. Line a baking sheet with foil and roast the peppers, tomatillos and onions until evenly blistered and blackened in some spots, 10 to 12 minutes.
Allow to cool completely, then stem, peel, seed and roughly chop. Set aside.
Lower the oven to 350º and grease an 8-inch square baking dish.
In a medium bowl, whisk together the cornmeal, flour, sugar, salt, baking powder, baking soda and cumin.
In a blender, purée the the buttermilk, butter and egg until smooth.
Mix dry ingredients, wet ingredients, roasted veggies and cheese torgether.
Pour the batter into the prepared pan and smooth the top with a rubber spatula.
Bake until golden brown and a toothpick comes out clean when inserted into the center, about 30 minutes.
Let cool completely before cutting into squares and serving.