Heat grill to medium-high and lightly brush with oil.
Carefully pound out both chicken breasts so they are 1/4-inch thick all the way around. Sprinkle cumin and salt on both sides of chicken, rubbing in all over.
Grill chicken 5 minutes on each side, turning once, or until chicken reaches an internal temperature of 160°. Remove, place on a serving platter, then let chicken rest 5 minutes until the internal temperature of 165° is reached.
While the chicken is cooking, whisk together all sauce ingredients in a small serving bowl (sauce consistency should be runny).
The chicken will serve as the "crust" of the pizza. Spread each pizza "crust" with salsa, then distribute the rest of the toppings, as desired. Drizzle sauce over each pizza and serve the rest alongside the pizzas. Serve.