Preheat the oven to 400°F.

In a skillet over medium heat, warm the oil and brown the ground beef, breaking it apart as it cooks, about 5 minutes.

Mix in the tomato paste and cook for 3 minutes, then add the chili beans with their liquid. Simmer for 10 minutes, seasoning with salt and pepper to taste.

Remove the beef mixture from the skillet and set aside. Wipe the skillet clean.

Layer the bottom of the skillet with tortilla chips, sprinkle a generous amount of cheese, and spoon some beef mixture on top. Repeat layers until all ingredients are used, finishing with a cheese layer.

Bake in the preheated oven until the cheese is melted and bubbly, about 10 minutes.

Garnish the baked nachos with chopped tomatoes, scallions, and dollops of sour cream before serving.