Preheat oven to 450 degrees F (232 C), and add lemon juice to almond milk to make "vegan buttermilk." Set aside.
In a large mixing bowl, whisk together dry ingredients.
Add cold butter and use fingers or a pastry cutter to combine the two until only small pieces remain and it looks like sand. Work quickly so the butter doesn’t get too warm.
Make a well in the dry ingredients and, using a wooden spoon, stir gently while pouring in the almond milk mixture 1/4 cup at a time. You may not need all of it. Stir until just slightly combined – it will be sticky.
Turn onto a lightly floured surface, dust the top with a bit of flour and then very gently turn the dough over on itself 5-6 times – hardly kneading.
Form into a 1-inch thick disc, handling as little as possible.
Use a 1-inch thick dough cutter or a similar-shape object with sharp edges (such as a cocktail shaker) and push straight down through the dough, then slightly twist. Repeat and place biscuits on a baking sheet in two rows, making sure they just touch – this will help them rise uniformly. Gently reform the dough and cut out one or two more biscuits – you should have 7-8.
Next brush the tops with a bit more of melted non-dairy butter and gently press a small divot in the center using two fingers. This will also help them rise evenly, so the middle won’t form a dome.
Bake for 10-15 minutes or until fluffy and slightly golden brown. Serve immediately. Let remaining biscuits cool completely before storing them in an airtight container or bag.