Grease and line a standard 9-inch x 5-inch loaf pan, and set it aside.

In the bowl of a stand mixer fitted with the paddle attachment, whisk together the flour, xanthan gum, sugar, yeast, and cream of tartar.

Toss in the salt and whisk again to combine.

Add the vinegar, eggs, warm milk, and butter to the dry ingredients.

Beat on medium-low speed for 30 seconds, then switch to medium-high speed for at least 2 minutes. Scrape down the sides and beat on high for another 2 minutes.

Move the dough into the prepared loaf pan, pressing it firmly into the corners. Smooth the top with a moistened spatula.

Cover the pan with lightly greased plastic wrap and place it in a warm, draft-free spot to rise until it reaches the top of the pan (about 1 hour or longer).

When it’s puffed up beautifully, preheat the oven to 375°F.

Remove the plastic wrap and score the loaf down the center at a 45° angle, cutting about 1/4 inch deep.

Bake for 25 minutes, rotate the pan 180°, and bake for another 20 minutes.

For a soft crust, wrap in aluminum foil and bake an extra 5-10 minutes, or until it reaches at least 190°F inside.

Remove from the oven, let it cool on a wire rack, and slice to serve.