Preheat oven to 350°F. Prepare a 9x13 inch baking tray with baking paper.
Add almond flour, baking powder, and salt to a large mixing bowl. Stir to combine.
Beat one egg with a whisk in a small bowl. Add the beaten egg, almond milk, and apple cider vinegar to the flour mixture.
Stir very well until a smooth batter is formed. Set aside.
Separate the whites of the four remaining eggs and place them in a medium bowl. Beat the egg whites with an electric mixer until soft peaks form.
Add the beaten egg whites to the dough and slowly stir to incorporate. It will lose a lot of air, but some will remain, making the focaccia very fluffy.
Place the batter in the prepared baking tray. Spread it evenly. It doesn’t need to go up to the edges as it’ll spread a bit once in the oven.
In a small bowl, mix the olive oil with rosemary leaves and let it sit for 5 minutes.
Brush the rosemary oil all over the focaccia. Arrange some halved cherry tomatoes and salt flakes on the top.
Bake for 20–25 minutes or until a toothpick inserted comes out clean.
Let the focaccia cool before serving or transferring to another container.
Keep the leftovers in an airtight container in the fridge for up to 7 days.
If reheating later, warming in the oven provides the best texture.
Rosemary is the most traditional herb when making focaccia, but there are other delicious alternatives. You can top your focaccia with crushed garlic and parmesan or caramelized onion and arugula (add the arugula after baking the focaccia).
Use good quality, cold-pressed, extra virgin olive oil for the best results.