Preheat oven to 350° F. Grease a 9” x 5” loaf pan and line with parchment with over hang in at least one direction for easy removal.
Combine flour, baking powder, baking soda, sweetener, and salt in a large bowl. Mix well.
Make a well in the center and add oat milk, oil, and vanilla. Stir until mostly incorporated.
Add in the lemon juice and zest and stir until completely smooth. You have to work fast from this point because the acid will start reacting with the baking soda immediately.
Scrape into prepared pan and level out.
Bake for 45-55 minutes until golden brown on the edges. Make sure it is set in the center and a toothpick inserted comes out clean.
Allow to cool in the pan for at least 20 minutes before transferring to a cooling rack.
Once the loaf is cool, make the glaze.
Combine the powdered sugar with just enough lemon juice to make a thick but pourable glaze into a measuring cup or small mixing bowl with a spout.
Drizzle over the loaf and allow to set.