Begin by whisking together 1.5 cups of sugar and 2 Tbsp. of cinnamon together in a bowl and set aside.
Next, melt and brown 1 stick of butter in a pan. Be careful not to burn the butter.
Once melted, add the butter to the bowl of a stand mixer and add in 1/2 cup of sugar. Mix together on medium low until combined.
Add in eggs, vanilla, sourdough discard, and milk and mix until combined.
Next, add in flour, baking powder, and salt. Mix on low speed until combined. Do not over-mix.
Allow the dough to rest for 2-3 minutes.
While the dough is resting, add 16 oz. of coconut oil to a cast iron skillet. Heat the oil to 375° F.
Flour the workspace and scrape the dough onto the floured workspace. Add a little bit of flour over the dough and a rolling pin, and begin rolling out the dough until it is 3/4 of an inch thick.
Using a donut cutter, cut out your donuts.
Fry the donuts for 1-2 minutes per side until golden brown.
Once the donuts are done frying, add them to the boil of cinnamon sugar and coat them in the sugar. Be careful, not to burn your hands doing this.
Set them on a wire cooling wrack and allow them to cool slightly before eating.