To a 8x11" baking dish or large cast iron skillet, add butter and place in the oven to melt.
In a large bowl, add sourdough starter, sweetener, eggs, vanilla extract, and baking powder. Whisk until well combined and smooth. Watch to make sure the butter doesn't burn.
Take the dish with butter out of the oven and make sure the butter is evenly distributed around the dish.
Pour in batter and place in the oven to bake for 25-35 minutes or until the edges start to turn golden brown and a knife comes out clean when inserted.
Allow to cool for 5-10 minutes.
Notes
This recipe is pretty flexible. If you like a sweeter pancake, you could add a touch more sweetener, or dust it with powdered sugar.
Speaking of sweetener, sugar, honey or maple syrup will work. Usually, I try to use more unrefined sweeteners.
For a dairy-free version, swap out butter for coconut oil.
Bake on a cookie sheet (baking time will be slightly shorter) to make thicker type of crepe like pancake.