Every tortilla has two sides. The bottom goes against your hand, and the top is where you place the fillings. This rule applies to making enchilados, burritos, sopes and yes even tacos. Every good Mexican cook knows the difference and even children are taught how to hold the tortilla when adding fillings. This is especially important to keep the tortilla from breaking as it is rolled or folded.
When cooking the tortilla it is almost impossible to finish with both sides cooked the same. One side will be a bit thicker and cooked consistently. There will be no air bubbles and no scorched areas. This is the bottom side that will go against your hand.
The other side, will have thinner areas that are already breaking apart a bit, and there will be scorched areas. This is to top side to which you will add the fillings. The reasons are two fold. The scorched area will be hidden under the fillings and the tortilla will resist breaking apart on the outside after rolling or folding.
