If your kids love taco night, surprise them with a do-it-yourself taco bar that fits neatly into a lunch box.
Fold 1 slice roast beef inside each of 2 soft tortillas and sprinkle with cheese. Pack in the biggest compartment of the lunch box. Pack other compartments with guacamole, salsa, sour cream and other favorite toppings. Seal and send off to school.
Grate tomatoes on the largest holes of a box grater into a bowl all the way down to the skins. Discard the skins. Grate the onion into the tomato. Stir in olive oil. Season with salt, to taste. Serve with cilantro leaves on the side, or stirred in, if desired.
Scoop the flesh from the shell with a spoon into a medium bowl. Squeeze the lime juice over the avocado and stir to coat evenly. Add the salt. Use a fork to stir and mash into a chunky guacamole. Stir in tomatoes or fruit, if desired.