Make the cornbread: Preheat the oven to 450°F Coat the bottom and sides of a 10-inch cast-iron skillet with the vegetable oil; place skillet in oven to heat.
Whisk the eggs and buttermilk together in a large bowl. Add the cornmeal, baking soda, baking powder, salt, and jalapeños while stirring briskly. Pour the batter into the hot skillet. Bake for 15 minutes or until lightly browned. Cool on a rack; crumble into a bowl.
Make the salad: Combine the dressing mix, sour cream, and mayonnaise in a small bowl; set aside. Combine the tomatoes, bell pepper, and scallions in another bowl.
Place half the crumbled cornbread in the bottom of a large serving bowl. Spoon on half the pinto beans; top with half the tomato mixture, half the cheese, half the corn, and half the bacon. Spread on half of the dressing. Repeat the layers, ending with the dressing. Cover with plastic wrap and chill for at least 2 hours before serving.