Preheat oven to 350. Lightly oil an 8-inch cake pan and line the bottom with parchment paper. Lightly oil parchment paper and dust with flour, tapping out the excess.
In a liquid measuring cup, steep tea bags in hot water for 20 minutes.
While tea is steeping, add coconut oil and coconut sugar to the bowl of the stand mixer. Split the vanilla bean in half lengthwise using a paring knife. Use a small spoon to scrape the seeds out of each half and add to the coconut oil and sugar. Beat oil, sugar, and vanilla bean seeds together until light and fluffy, about 2-3 minutes. Add eggs, one at a time, scraping down the sides of the bowl when necessary.
In a mixing bowl, whisk together the flour, baking powder, baking soda, cinnamon, and salt.
Remove tea bags and gently squeeze tea bags to get as much liquid out before discarding. Add ¾ cup buttermilk plus enough extra so that the total amount of liquid measures 1 ¼ cup.
Gradually add the dry ingredients to the sugar mixture in three parts, alternating with the tea mixture, beginning and ending with the dry ingredients. Mix until the final portion of dry ingredients is just combined.
Pour batter into prepared cake pan and smooth with an offset spatula. In a small bowl, combine sliced almonds, coconut oil, coconut sugar, and cinnamon. Gently toss together until almonds are evenly coated. Scatter almonds on top of the cake.
Bake until almonds are lightly golden and tester comes out clean, about 35 minutes. Cool in pan 10 minutes before turning the cake out to finish cooling on a wire rack. Dust with confectioner’s sugar and serve with a dollop of mascarpone cream. This cake is best served the day it’s made, but it can be stored at room temperature in an airtight container for a couple days.
Notes: It’s important to use room temperature eggs and buttermilk in order to avoid the coconut oil seizing.