Make the sourdough sponge the previous night by mixing in a large bowl the sourdough starter with the flour, sugar, nondairy milk and apple cider vinegar. Cover with plastic wrap and allow the batter to stand overnight. In the morning, it will be puffy and will have visible bubbles in it.
Before making the pancake, preheat the oven to 450 degrees.
Add the baking soda, applesauce and flax eggs to the sourdough sponge and mix.
Heat a 10-inch cast iron pan on the stovetop. Add 1 tbsp vegan butter or oil. Swirl it around to spread.
Arrange half the pear slices on the skillet. You can either do a decorative pattern or just lay them in. They shouldn't overlap. Let the pears cook for a couple of minutes, without disturbing them.
Turn off the heat and pour half the pancake batter over the pears. Immediately place the pan in the oven and bake 15 minutes or until the pancake appears golden-brown and the sides are pulling away from the pan.
Being very careful while handling the hot skillet, flip the pancake upside down on a plate. Repeat one more time to make the second pancake.
Serve the pancake hot with a pat of vegan butter and maple syrup.