Crack an egg into a mug with a wide base. Alternatively, you can use a large ramekin for a smallish bun.

Microwave butter for 10-15 seconds to melt it. Once melted, pour over the egg and whisk well to aerate the mixture. The eggs should become slightly lighter in color.

Add in the almond flour, psyllium husk powder, baking powder, cream of tartar, and chicken broth.

Mix everything well to form a slightly doughy mixture, wiping off any excess stuck to the edge of the cup to make the top as uniform as possible.

Microwave for 60–75 seconds, depending on the microwave. If it puffs up quickly, don't worry — it will reduce in size greatly once taken out. Once out, flip the mug over and tap it lightly against a plate to slide the bun out. Cut in half, toast, and enjoy!