Prepare a paste consisting of the oil, flour and chili powder. Add the water and stir in the pureed tomato, the tomato puree, cumin and garlic salt. This will form the enchilada sauce.
Transfer the sauce to a saucepan and heat over medium-high heat.
As the enchilada sauce simmers, heat the mince, capsicum and onion in a frying pan, until the beef is brown and the onions are soft and semi-transparent.
Fill the tortillas on a plate with the filling, and fold them, by starting with opposite corners. Put a little bit of sauce inside each tortilla. Place some cheese between the last two folds, and place the tortillas upside-down in a dish. The cheese should melt, holding the tortillas shut.
Sprinkle the remaining cheese, and any remaining filling on top of the enchiladas. Pour the rest of the sauce evenly over the burritos.
Place the dish in the oven for 10 minutes, then serve.
Lift the enchilada out of the dish carefully with a spatula.