Place 1 cup flour blend and salt and pepper in a bowl and combine. Stir in 1 cup beer until ingredients are well blended. If batter is too thin, add an additional tablespoon flour. If too thck, add an additional tablespoon beer.
Peel onion and cut off the ends. Slice onion into ¼-inch to ½-inch thick slices. Break apart the rings and sprinkle them with flour blend.
Pour oil into a frying pan, just deep enough to cover rings. Heat oil to medium-high until a drop of beer batter sizzles when placed in pan.
Dip floured onion rings into beer batter and fry in oil on medium heat until golden brown. Add more oil if needed between rings. (Wait for oil to get sizzling hot before frying.)
Place fried rings on paper towels to drain. Keep onion rings warm until all are fried.
*TIP For best results, use a flour blend of equal parts garbanzo flour and fava bean flour.