For the cake: Heat oven to 350 degrees Fahrenheit. Grease an 8-inch round cake pan and line the bottom with parchment paper.
In a food processor, grind 1 cup pIstachios into a meal consistency, careful not to overprocess or you will have butter! In a medium bowl, combine almond flour, ground pistachios, baking soda, salt, and arrowroot starch.
Wipe out your food processor, add honey and 3 kumquats. Process until smooth.
In a small bowl, whisk honey, milk, olive oil, vanilla extract, and eggs until combined. Add the liquid mixture to the dry ingredients, whisking until smooth.
Pour batter into prepared pan and bake for 40-43 minutes, or until a toothpick comes out clean. Due to the honey, the cake will brown more quickly. Place a piece of foil over the cake in about the last 10 minutes of baking to prevent burning. Once cool, loosen edges of cake before transferring to plate or cake stand.
For the honeyed kumquats: Starting at the round end, cut a cross into each kumquat down to a 1/4 inch of the other stem end. In a small saucepan, combine honey and water, bring to a boil, stirring frequently until honey dissolves. Add the vanilla extract and kumquats. Simmer for about 8 minutes or until kumquats are tender, stirring often. Remove kumquats with a slotted spoon, place on plate until ready to use. Continue to gentle boil syrup until it reduces to about 1 1/4 cup. Remove from heat, allow to cool, then place in an airtight container until time to serve.
For the mascarpone cream: While the cake is cooling, combine mascarpone, coconut cream, vanilla extract, cane sugar in a medium bowl. Mix on medium speed until ingredients are incorporated and mixture is smooth. Refrigerate until ready to assemble cake.
Assembling cake: Roughly chop 1/3 cup pistachios. Spread mascarpone cream over top of cake, spinkle with chopped pistachios. Place some or all of honeyed kumquats on top of cake as desired. Serve each slice of cake topped with kumquats and drizzled with kumquat syrup. Cake best served the day it is made.