Preheat the oven to 350°F (177°C). Line an 8.5x4.5-inch loaf pan with parchment, letting the paper overhang the long sides for easy removal.

In a large bowl, cream together the softened butter and sweetener using a hand mixer until light and fluffy.

Add eggs one at a time, mixing briefly after each until combined. Stir in the vanilla extract.

Lower mixer speed and gradually beat in almond flour, baking powder, and salt until mostly combined. If using, sprinkle xanthan gum over the batter and blend briefly until just mixed. Batter will be thick and creamy.

Scrape down the bowl sides and pour the batter into the prepared loaf pan. Smooth the top and round it slightly with a spatula.

Bake for 25–30 minutes until the top turns golden. Then tent the pan with foil and bake another 20–30 minutes, or until a toothpick inserted into the center comes out clean.

Remove from oven and let the loaf cool in the pan. After 10–15 minutes, use the parchment overhang to lift it out and let it finish cooling on a rack. Slice when cooled completely.