Preheat the oven to 350 degrees F (175 degrees C). Line an 8-inch square pan with parchment paper.
Mix cream cheese and stevia together in a bowl using an electric mixer until creamy smooth. Mix in egg and vanilla extract until fully combined.
Bring a saucepan of water to a simmer. Top saucepan with a heatproof bowl large enough to stay above the water. Combine butter, stevia, cocoa powder, and salt in the bowl. Cook and stir until melted and fully combined, 1 to 3 minutes. Remove from heat and cool until bowl is safe to handle. Whisk in 1 egg at a time, stirring vigorously, until mixture becomes pudding-like. Add almond flour and continue to whisk brownie mixture until blended.
Pour 2/3 of the brownie mixture into the bottom of the prepared baking pan. Add cream cheese mixture. Top with dollops of remaining brownie mixture and use a knife to create a swirled design.
Bake in the preheated oven until set but still slightly jiggly, about 25 minutes. Cool before serving.