Heat oven to 425°F (220°C). Line a baking sheet with foil or parchment and set a wire rack on top. Spray the rack lightly with oil—this is your crunch insurance.
Peel onions and slice into 1/2-inch rings. Separate into individual rings. Save the tiny inner rings for a snack-sized batch or chop for another recipe—no ring left behind.
Set up three bowls:
Toss onion rings in the flour mixture to lightly coat. Shake off excess—too much flour blocks adhesion.
Dunk floured rings into the egg mixture, let excess drip, then press into the breadcrumb mix, coating thoroughly. Use one hand “wet,” one hand “dry” to keep things sane.
Arrange coated rings on the prepared rack with space between each. Crowding kills crunch, and we don't do soggy.
Lightly spray the tops with oil. This helps the breading turn shatter-crisp and golden.
Bake for 12–15 minutes. Flip, spray again, and bake another 8–10 minutes until deeply golden and crisp. Thicker rings may need an extra 2–3 minutes.
Sprinkle with a pinch of salt while hot. Serve immediately with your favorite dip. Consider a squeeze of lemon if you're feeling fancy.