2) In a food processor combine the sour cream, mayonnaise, tomatoes, red peppers, lime juice, 1/2 tsp of the pepper, 1 tsp of the salt, the white wine and minced garlic.
3) Slice the onions 1cm thick, remove the dark exterior and separate into rings. Soak the rings in buttermilk for 1 hour.
4) Combine 140g of the flour, the remaining salt and pepper and the garlic and mix thoroughly. In a medium bowl combine the beer and the remaining flour and mix thoroughly.
5) Remove the onion rings from the buttermilk and shake off the excess. Dredge in flour and shake off the excess, then dip in the beer batter. Drop some onion rings in the oil and deep fry, being sure not to crowd the rings as they will stick together. When golden, remove and drain on paper towels.
6) Garnish with grated Parmesan and serve.