Best Frito Pie

In a large pot over medium heat, heat oil. Add half onion and cook until soft, about 5 minutes. Stir in garlic and cook until fragrant, about 1 minute more, then add tomato paste, stirring to combine. Add ground beef and cook until no longer pink. Drain fat and return to heat. Add chili powder, cumin, oregano, cayenne, and season generously with salt and pepper. Pour in crushed tomatoes, pinto beans, and green chili and bring chili to a boil. Reduce heat and simmer 20 minutes. Season with more salt and pepper, if necessary. Build Frito pie: open bag(s) and ladle in chili. Top with cheddar, remaining chopped white onions, jalapeños, and sour cream if using.