Preheat the oven to 350°F.
Drain and rinse the red kidney beans and mix them with the tomato sauce. Heat them up in a pot for a few minutes.
Pour in an oven safe dish, stick the tortilla chips into it. Sprinkle cheese and bake for about 10 minutes, until the cheese is melted. Watch out because the tortilla chips can burn pretty fast.
In the meantime, mash the avocado in a bowl, add lemon juice and salt to taste. Place the sour cream next to it.