dente, so there\u2019s some texture and a slight hit of sharpness yet not enough that you\u2019ll taste onion the rest of the day. Remove the onion from the butter and drain on a paper towel."},{"@type":"HowToStep","text":"While the onion cooks, make a horseradish sauce. In a bowl, mix the grated horseradish with the buttermilk and a pinch of salt. Stir to combine and refrigerate until ready to use."},{"@type":"HowToStep","text":"Before you begin cooking the burgers, get the buns toasting. Heat a cast-iron 