Gather bratwurst, beer, onion, butter, and buns
Slice the onion
Melt butter in a skillet or pot over medium heat
Add the onion and cook until softened
Add the bratwurst to the skillet or pot
Pour in enough beer to partially cover the brats
Bring to a gentle simmer
Cook the brats until heated through and nearly done
Remove the brats from the beer
Grill or pan-sear the brats until browned
Toast the buns if desired
Serve the brats in buns with the cooked onions
Add mustard or other toppings if desired