Preheat the oven to 200°C/400°F. Lightly grease a 9x9 inch (21x21cm) casserole dish
Heat the oil in a large skillet and add the onion, garlic, bell peppers, cumin, paprika and chilli powder. Stir for a few minutes until the vegetables are soft and the spices are cooked, about 3-5 minutes. Add the beans, corn and tomato sauce. Stir to combine, season with salt to taste and set aside to cool a bit.
Spread half the tomato sauce mixture on the bottom. Then add half of the tortilla strips, allow them to overlap. Next, add half of the white sauce, spreading out evenly. Then sprinkle over half of the non-dairy cheese.
Repeat adding another layer of remaining tortilla strips, tomato sauce, white sauce and finish with the rest of the cheese.
Cover the baking dish with aluminum foil or baking paper and bake for 15 minutes. Remove the foil and bake for approx. 5-8 minutes longer until the casserole has cooked through and the cheese is perfectly melted.
Allow to cool for 3-5 minutes before cutting into squares.