For enchiladas:
1 large white onion, cut crosswise into 1/2-inch-thick rounds
2 red bell peppers, quartered
3/4 pound medium zucchini, cut lengthwise into 1/4-inch-thick slices
12 (6-to 7-inch) soft corn tortillas
1/2 cup vegetable oil
6 ounces crumbled queso fresco or ricotta salata
For pumpkin-seed salsa:
1 tablespoon finely chopped fresh serrano chile, including seeds
2 garlic cloves, minced
1 teaspoon ground cumin
1 1/3 cups raw green (hulled) pumpkin seeds (pepitas)
1/2 cup vegetable oil
2 cups chopped cilantro
1 1/2 cups water
For tomato salsa:
2 medium tomatoes, chopped
1/4 cup finely chopped white onion
2 teaspoons finely chopped fresh serrano chile, including seeds
2 tablespoons fresh lime juice
Start enchiladas:
Prepare a gas grill for direct-heat cooking over medium heat; see Grilling Procedure .
Preheat oven to 350°F .
Secure each onion round with a wooden pick for grilling. Oil grill rack, then grill vegetables, covered, turning occasionally, until tender (6 to 8 minutes for bell peppers and zucchini; 10 to 12 minutes for onion), transferring to a bowl.
Wrap tortillas in stacks of 6 in foil and heat in oven, about 15 minutes.
Meanwhile, make pumpkin-seed salsa:
Cook chile, garlic, cumin, and pumpkin seeds in oil in a 10-inch heavy skillet over medium-high heat, stirring, until seeds pop, 4 to 5 minutes. Transfer 3 tablespoons seeds with a slotted spoon to a bowl and reserve. Purée remaining seeds and oil with cilantro, water, and 1/2 teaspoon salt in a blender until smooth.
Make tomato salsa:
Stir together tomatoes, onion, chile, lime juice, and 1/4 teaspoon salt.
Assemble and fry enchiladas:
Cut vegetables into strips. Spread 2 teaspoons pumpkin-seed salsa on each warm tortilla and top with some of grilled vegetables, then roll up. Heat oil (1/2 cup) in a 12-inch heavy skillet over medium-high heat until it shimmers. Fry enchiladas, seam side down first, in 2 batches, turning once, until lightly browned and heated through, about 2 minutes per batch. Transfer enchiladas to plates, then drizzle with remaining pumpkin-seed salsa and sprinkle with reserved seeds and cheese. Serve with tomato salsa.