Whisk egg, buttermilk, melted butter, orange zest, goat cheese, and a pinch of salt until smooth. Chill.
In a separate bowl, whisk flour, baking powder, baking soda, salt, and sugar.
Fold wet into dry just until combined. Batter should be thick and scoopable. Chill at least 30 minutes (or overnight).
Simmer honey until very hot. Stir in chili flakes and kumquats. Cook on low until kumquats are tender and honey thickens, 10–15 minutes. Cool until glossy.
Mix sugar and dried scallions. Set aside.
Heat oil to 350°F. Scoop batter into oil and fry until puffed and golden, 2–3 minutes per side. Drain on paper towels.
Toss warm donuts in scallion sugar. Plate and drizzle generously with kumquat chili honey.