Place the garlic, chilli powder, oil, paprika and cumin in a bowl and mix together. Rub all over the steak, then place in a shallow dish. Cover with clingfilm and leave to marinate in the refrigerator for at least 2 hours and preferably overnight.
Season the meat well. Heat a griddle pan until smoking hot, add the steak and cook for 3–5 minutes on each side until browned and cooked to your liking. Remove from the pan and cut into thin slices.
Make the salsa by tossing together all the ingredients in a bowl.
When ready to serve, heat a dry nonstick frying pan until hot, add 1 tortilla and cook for 30 seconds until pliable. Remove from the heat and spoon a little cooked rice and warmed beans into the centre. Add some strips of steak and top with some tomato salsa, lettuce, cheese, soured cream and coriander. Fold up the outside edges, squashing down the filling a little if necessary, and roll over so the filling is completely enclosed. Repeat with the remaining tortillas.