Preheat oven to 450°.
Roll prepared pizza dough into a 12-inch circle on a floured surface. Place the dough on a 12-inch pizza pan or baking sheet coated with cooking spray and sprinkled with 1 tablespoon cornmeal. Crimp edges of dough with fingers to form a rim.
Place onion rings in a large bowl. Lightly spray with cooking spray, and sprinkle with 1/4 teaspoon salt and 1/8 teaspoon black pepper; toss well to coat. Arrange onion on a jelly roll pan coated with cooking spray. Bake at 450° for 15 minutes, stirring halfway through; cool.
Place poblano chile on a foil-lined baking sheet, and broil 3 inches from heat 8 minutes or until blackened and charred, turning after 6 minutes. Place in a zip-top heavy-duty plastic bag, and seal. Let stand 15 minutes. Peel and discard skins. Cut a lengthwise slit in poblano chile; discard seeds and stem. Cut roasted poblano chile into thin strips. Sprinkle strips with remaining 1/4 teaspoon salt and 1/8 teaspoon black pepper, and set aside. Reduce oven temperature to 500°.
Place chipotles in a food processor or blender, and process until smooth. Spread 1/2 tablespoon chipotle puree over the pizza crust using back of spoon. Reserve the remaining chipotle puree for another use. Arrange the chile strips in an even layer over the pizza crust; top with onions, tomatillos, cheddar, and queso fresco. Bake at 500° for 17 minutes or until crust is golden. Remove pizza from oven, and sprinkle with cilantro and pumpkinseeds.