Make the roasted garlic, pickled onions, and blanched asparagus ahead, then top and bake the pizza before serving. If you don't have a pizza stone, preheat a rimless baking sheet while you prepare the pizza. This will help form a crisp crust similar to that achieved on a pizza stone. Refrigerate leftover pickled onions in an airtight nonreactive container for up to two weeks. Use them to add tang to salads or sandwiches.
Remove white papery skin from garlic head (do not peel or separate the cloves). Coat garlic with cooking spray. Wrap garlic head in foil. Bake at 400° for 45 minutes or until tender; cool 10 minutes. Separate cloves; squeeze to extract garlic pulp. Discard skins. Combine garlic pulp and olive oil in a small bowl, stirring until smooth.
Preheat oven to 500°.
Place a pizza stone on bottom oven rack. Preheat pizza stone 30 minutes.
Combine onion, vinegar, and 2 teaspoons salt in a bowl; let stand 20 minutes. Remove 1 cup onion mixture with a slotted spoon; set aside. Reserve remaining onion mixture for another use.
Cook asparagus in boiling water 2 minutes or until crisp-tender. Drain and rinse under cold running water; drain. Pat dry with paper towels.
Divide dough in half. Working with 1 half at a time (cover remaining dough to keep from drying), roll dough into an 11-inch circle on a lightly floured surface. Place dough on a baking sheet (or jelly-roll pan) sprinkled with 1 tablespoon cornmeal. Spread half of garlic mixture over dough. Top with 1/2 cup onion mixture and 3/4 cup asparagus, leaving a 1-inch border. Sprinkle with 6 tablespoons cheese. Slide topped dough onto preheated pizza stone, using a spatula as a guide. Bake at 500° for 8 minutes or until cheese melts and crust is golden brown. Remove from pizza stone using pizza peel. Place pizza on a cutting board; sprinkle with 1/8 teaspoon salt. Cut into 6 wedges. Repeat procedure with remaining dough, 1 tablespoon cornmeal, garlic mixture, 1/2 cup onion mixture, 3/4 cup asparagus, 6 tablespoons cheese, and 1/8 teaspoon salt.