Meanwhile, place butter, peanut butter, and swerve into a stand mixer bowl. Use a whisk attachment to cream and aerate the ingredients, about 3-4 minutes. The mixture should be light and form soft peaks.
Add in eggs one at a time, continuing to beat with each addition. Add coconut flour, vanilla, baking powder, cinnamon, and whisk slowly until well incorporated.
Pour batter into the prepared bundt pan and bake for 30 minutes.
It's important to note that this cake is sweetened with a keto-friendly sweetener called Swerve. If you haven't used this before, many of my dessert recipes utilize it and it's worth checking into. You can use other options, but they may not substitute straight across amount wise.
Not all natural peanut butters are created equal, so make sure to take a moment to read over the nutrition label before picking one.