Lightly spoon flour into dry measuring cups; level with a knife. Follow manufacturer's instructions for placing flour and the next 4 ingredients (flour through salt) into bread pan, and select dough cycle; start bread machine.
Remove dough from machine (do not bake). Turn the dough out onto a floured surface, and knead for 30 seconds. Cover dough; let rest 10 minutes.
Preheat oven to 425°.
Divide dough into 6 equal portions. Roll each portion into a 9-inch circle on a lightly floured surface. Cover baking sheets with parchment paper, and place dough rounds on pans. Lightly coat top of dough with cooking spray. Cover and let rise in a warm place (85°), free from drafts, 15 minutes or until puffy.
Divide the onions and pepper evenly among dough rounds. Bake at 425° for 10 minutes. Remove from oven; drop 3 teaspoonfuls of cheese onto each round. Arrange 1 ounce smoked salmon on top of each pizza, and divide capers evenly among pizzas.
Bake the pizzas an additional 8 minutes or until the cheese melts. Serve pizzas with lemon wedges.