Whisk together sriracha and mayonnaise in a small bowl. Cover and place in the refrigerator.

Add oil to a large pot (I used a 5.5 quart French oven), about 1.5 inches of oil. Heat to 350 degrees F. Line a baking sheet with foil and paper towels.

Combine flour, cayenne, salt, pepper in a large mixing bowl.

Peel and rinse the onions. Quarter them and separate into petals. Discard smaller center pieces. Cut pieces that are too wide in half.

Take 1/4 cup of flour mix and place in separate dish. Coat onion petals in dry flour mixture.

Pour beer into remaining flour mixture (large mixing bowl). Mix with a fork but don't overmix. (Batter will be lumpy.) Coat onion petals in batter. Shake excess batter off.

Fry 2-3 minutes until golden brown. Use tongs to remove from oil.

Serve immediately with spicy mayo dipping sauce. Serve cold.