Preheat your oven to 350°F and lightly grease a large oven-safe ramekin with a small amount of coconut oil or avocado oil spray.
In a medium mixing bowl, whisk together the chocolate protein powder, cocoa powder, oat flour, baking powder, and sea salt until no lumps remain.
Add the egg whites, Greek yogurt, and vanilla extract to the dry ingredients, stirring until the batter is smooth and well-combined.
Pour approximately two-thirds of the batter into the prepared ramekin.
Place the dark chocolate chips in a cluster directly in the center of the batter, then cover them with the remaining cake batter.
Bake for 12 to 15 minutes, or until the edges are firm and the top is set but the center still has a slight jiggle.
While the cake bakes, place the raspberries and lemon juice in a small saucepan over medium heat, mashing them with a fork as they warm until they form a liquid sauce.
Strain the raspberry mixture through a fine-mesh sieve to remove seeds, creating a smooth coulis.
Remove the cake from the oven, let it cool for 2 minutes, and drizzle the fresh raspberry coulis over the top before serving warm.