Grease an 8-inch baking round and line it with a circle of parchment paper.
In a large bowl, using a handheld mixer or stand mixer, cream the ¾ cup unsalted butter and 1 cup light or dark brown sugar together on medium speed until light and fluffy, about 3 minutes. Beat in the 2 eggs and 2 teaspoons pure vanilla extract on medium-high speed until combined. Scrape down the sides and bottom of the bowl as needed.
In a separate bowl, whisk together the 2 cups oat flour, 1 teaspoon baking soda, and ½ teaspoon fine sea salt. Beat the dry ingredients into the wet ingredients on low speed until combined. Fold in the 1 ½ cups semi-sweet chocolate chips.
Press the batter evenly into the prepared pan and let it rest for 20 minutes. The batter will be thick. Then, preheat the oven to 350°F and bake for about 25-30 minutes until the surface of the cake is golden brown and a tester comes out mostly clean.
Transfer the pan to a wire rack to cool completely. Place the cake on a plate and cut wedges to serve, or cut and serve it directly from the pan.
Notes
Rest the batter. As always, resting a gluten-free batter makes the final result so much better! For this recipe, there's no need to chill the dough, but it does benefit from resting for about 15-20 minutes before baking.
Use room temperature butter. Leave the butter out on the counter to soften for an hour, or zap it in the microwave for 15 seconds before mixing with the brown sugar.
Add candy. We discussed adding other types of chocolate above, but what about candy? Try mini M&M's, chopped peanut butter cups, or toffee instead of chocolate chips.
Vegan - Use softened non-dairy butter for the unsalted butter, and use 2 flax eggs for the eggs.
Finish with frosting - Make a simple chocolate icing or chocolate buttercream as mentioned above, or top with salted caramel frosting or even a maple glaze!
Marshmallows - Go for a s'more's vibe and fold in ½ cup of mini marshmallows.
Other chocolate - Try milk chocolate chips or white chocolate chips, or use mini chocolate chips.
Nuts - Toss in 1 cup of chopped walnuts with the chocolate chips!