Combine the flour, salt and pepper in a small bowl, add the onion, toss until well coated.
Add 3 to 4 inches of oil to a saucepan, use a deep fry thermometer to bring the oil to 375, adjusting heat to maintain that temperature.
Drop the onions in the oil, fry until golden brown, about 4 minutes.
Remove from oil, drain on a wire rack or paper towels.
In a pan with a lid add the brats and the beer, cover and simmer until the brats are cooked through, remove from pan.
Preheat the grill to medium high.
Add the brats, peaches, red onion and jalapenos, grilling all until grill marks appear on all sides.
Chop the peaches, onion and cilantro, add to a bowl along with the cilantro, toss to combine.
Add the brats to the buns, top with peach salsa and fried onions.