If you want a cake that isn't going to spike blood glucose, you not only need to cut out the sugar (or at least most of it), but the white flour, too.
Although this recipe is posted on the website of a commercial product, I've made the recipe and it's very good. It calls for a combination of almond and coconut flours.
Chocolate Layer Cake with Whipped Chocolate Ganache Frosting | Swerve Sweetener
Here's another that I've made:
Sugar-Free Low Carb Chocolate Tiramisu Cake Roll
Of course, there is always cheesecake, too. Cream cheese is naturally low carb. I make mine with an almond flour crust and use erythritol for the sweetener.