In a bowl mix flour, baking powder, beer and House Seasoning together. Let rest on the counter for 15 minutes to 3 hours.
Preheat oil in deep-fryer to 350 degrees F.
Slice 3/4-inch to 1-inch off the top of the onion. Peel off the skin. Cut a base out of the bottom but leave the root intact. Slice the onion in half, then into quarters, then into eighths. Continue until you've cut the onion 16 times. Slicing the onion in this way creates "petals". Do not cut all the way down to the bottom. This will keep the "flower" together. Spread the "petals" of the onion apart. Soak the onion in ice water to help separate the petals.
Dip the onion in the beer batter. Separate the "petals" and get the batter between them.
Fry the onion right side up in the oil for 10 minutes or until it turns golden brown. Remove the onion with a spider from the fryer and let drain on a sheet tray lined paper towels.
Mix ingredients together and store in an airtight container for up to 6 months.