Combine all spices in an airtight container and shake to blend.
Shape ground beef into 4 patties 3/4-inch thick. Press 1 tsp. of the spice mix evenly into both sides of each patty. Store remaining spice mix in airtight container for future use.
Heat a large heavy nonstick skillet 5 minutes over medium heat until hot. Add patties to skillet and cook 12-15 minutes, turning once, until centers are no longer pick and juices show no pink color (160°F internal temperature).
Line bottom of each bun with lettuce and tomato. Top with burger and spoon ranch dressing evenly over burgers. Sprinkle with French fried onions and close sandwiches.