Heat the oil in a deep pan and braise the finely chopped onions for 3 min. Add the cumin, coriander, paprika and cayenne pepper. Cook while stirring nonstop for 30 seconds or until the spices release their aroma.
Add the mince and stir with a wooden spoon for about 8 min. or until the mince is braised well. Add 14 oz (400 g) finely chopped fresh or canned tomatoes. Let it cook, stirring from time to time, until the sauce thickens.
Make the tortillas/tacos according to package directions. Put some beef, and iceberg lettuce pieces on top in each taco shell. Finish off with a chopped tomato and sprinkle generously with grated cheddar.