Zucchini-Blossom Quesadillas

Cook onion, garlic, and 1/2 teaspoon salt in oil in a large heavy skillet over medium heat, stirring, until onion is softened. Add tomato and cook, stirring occasionally, until tomato breaks down, 3 to 5 minutes. Add blossoms and 1/4 teaspoon salt, then cover and cook, stirring occasionally, until tender, 4 to 5 minutes.
Combine tortilla flour, water, and 1/4 teaspoon salt in a large bowl and knead until a uniform dough forms, about 1 minute.
Pinch off enough dough to form a 1 1/2-inch ball and transfer to a plate; dough should be moist but not sticky. If necessary, knead in a little more tortilla flour or water. Form remaining dough into about 13 (1 1/2-inch) balls, transferring to plate, and cover with plastic wrap.
Press 1 ball of dough between plastic squares in tortilla press to form a 5 1/2- to 6-inch tortilla (less than 1D16 inch thick). Peel off 1 plastic square, then, holding tortilla in your palm, put 1 rounded tablespoon cheese (1/2 ounce) on one side of tortilla and spread 1 rounded tablespoon filling in a flat layer over cheese, leaving a 3/4-inch border. Fold tortilla in half, using plastic square as an aid, and pinch edges to seal, flattening slightly.
Make more quesadillas in same manner, arranging them in 1 layer and covering with plastic wrap.
Very lightly oil comal (or pizza pan), then heat over medium-high heat until hot, about 2 minutes. Cook quesadillas, 3 at a time, until edges loosen from comal and brown spots appear on underside, 2 to 4 minutes, then turn over and cook, gently pressing quesadillas flat with a metal spatula if necessary, until brown spots appear on underside, 2 to 4 minutes more. Serve immediately with salsa on the side.