Number of People
1. Fill fryer's removable bowl with enough oil to sit between the MIN and MAX level; preheat fryer to 356F/180C. Set fryer basket aside.
2. Slice onions crosswise, just over 1/4-inch thick and separate into rings; toss rings with 2 tbsp flour to coat.
3. Whisk remaining flour, cornstarch, baking powder and salt in a large bowl; whisk in beer until just a few lumps remain.
4. Add a small batch of rings to the batter to coat; holding bowl close to fryer, use tongs to remove rings and place in a single layer in fryer. Fry for 2 minutes without turning. Turn and fry for 1 minute or until evenly golden.
5. Use a slotted spoon to transfer to a paper towel-lined baking tray. Repeat with remaining onion rings and batter. (Hold cooked onion rings in a 250F/120C oven while frying remaining batches.)
6. Sprinkle with coarse salt before serving (if using). Serve with ranch dip (if desired).