Set a rack in the upper third of the oven and pre-heat the broiler on high. Cover a baking sheet with aluminum foil and lightly coat with oil. In a bowl, combine the chili powder, oregano, salt, and pepper. Add the fish and rub the spices all over. Transfer to the prepared baking sheet. Lightly spray the fish with cooking spray. Broil just until the fish is cooked through and charred in spots, 5–7 minutes, depending on the fish you’re using. To serve, smear the tortillas with some Greek yogurt or sour cream. Add broiled fish and a few spoonfuls of salsa. Garnish with microgreens, green onions, and cilantro.