The lasagne can be assembled 1 day ahead. Cool the tomato salsa before assembling. Cover dish tightly with plastic and refrigerate until needed. Bake as directed in recipe, allowing an extra 5 to 10 minutes baking time and checking the lasagne is piping hot in centre before removing from oven. The assembled but uncooked lasagne can be frozen for up to 3 months. Wrap dish tightly in double layer of plastic and a layer of aluminium foil. Thaw overnight in fridge and cook as above. Leftovers should be covered and refrigerated as soon as possible. To reheat, put individual slices in ovenproof dish, cover with foil and reheat in oven preheated to 350 degrees F for 15 to 20 minutes. Check the lasagne is piping hot before serving. Wedges of leftover lasagne can be frozen for up to 2 months, tightly wrapped in plastic wrap and then either in foil or in resealable bag. Thaw overnight in refrigerator and reheat as above.