Place the tomato chunks in a large saucepan; fill the saucepan with enough water to cover the tomatoes. Cook over medium heat until the tomatoes are soft. Let cool slightly.

Puree the tomato chunks, along with 1 cup of the water they were cooked in, until smooth.

Pour the tomato puree into the same saucepan. (Discard the cooking liquid before you do.) Season the tomato salsa with salt and simmer over low heat until heated thoroughly.

While the tomato salsa is simmering, heat about 1/2 cup of vegetable oil in a medium skillet until very hot. Fry the corn tortillas, one at a time, in the hot oil for about 30 seconds on each side.

Dip the tortillas in the tomato salsa, then transfer to a plate.

Top each tortilla with 2 to 3 tablespoons of grated Queso Fresco and a little (or a lot of) chopped onion. Fold the tortilla in half as you would for a taco and transfer to a serving platter.

To serve, ladle a little more of the tomato salsa over the entomatadas and garnish with more Queso Fresco.