Prepare the Cake: Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan or line it with parchment paper.
Make the Cake Batter: In a large mixing bowl, combine almond flour, baking powder, and salt. In another bowl, whisk together the eggs, erythritol, melted butter, and vanilla extract until smooth and creamy. Gradually add the dry ingredients to the wet ingredients and mix until well combined. Stir in the heavy cream.
Bake the Cake: Pour the batter into the prepared cake pan and smooth the top with a spatula. Bake for 25-30 minutes or until a toothpick inserted into the center of the cake comes out clean. Allow the cake to cool in the pan for 10 minutes, then transfer it to a wire rack to cool completely.
Prepare the Toffee Glaze: While the cake is cooling, make the toffee glaze. In a saucepan, melt butter over medium heat. Add the heavy cream and bring to a simmer. Stir in the erythritol and cook for 3-5 minutes, allowing the mixture to thicken slightly. Remove from heat and stir in vanilla extract and a pinch of salt.
Assemble the Cake: Once the cake has cooled completely, pour the toffee glaze over the top. Use a spoon or spatula to spread the glaze evenly over the cake.
Serve and Enjoy: Slice and serve! You can enjoy the cake as is, or pair it with whipped cream or a cup of coffee for an extra treat.