Prep the pan: Preheat oven to 350°F (175°C). Line an 8.5 x 4.5-inch loaf pan with parchment, leaving overhang for easy lifting. Lightly grease the sides.

Mix the dry ingredients: In a large bowl, whisk almond flour, coconut flour, baking powder, salt, and flaxseed (if using) until no lumps remain.

Whisk the wet ingredients: In a separate bowl, whisk eggs, almond milk, melted butter (or oil), and apple cider vinegar until smooth.

Combine: Pour the wet mixture into the dry. Stir with a spatula until just combined. The batter will be thick but spreadable.

Flavor boost (optional): Fold in garlic powder or seasoning if using. Taste the batter (safe, no raw flour issues) to adjust salt or seasoning.

Fill the pan: Spoon batter into the lined loaf pan. Smooth the top with a spatula. For a neat dome, mound the center slightly.

Bake: Bake for 35–45 minutes until the top is golden and a toothpick comes out clean. If it browns too fast, tent with foil for the last 10 minutes.

Cool completely: Let the loaf cool in the pan for 10 minutes, then lift out using the parchment and cool fully on a rack before slicing.

Slice and serve: Use a serrated knife to cut into 12 slices. Enjoy warm or toasted with butter, avocado, or your favorite keto-friendly spread.