Preheat oven to 350 degrees F (175 degrees C). Wrap the bottom of a springform pan in aluminum foil and grease entire pan with coconut oil.
Stir walnuts, 3 tablespoons honey, and cinnamon together in a bowl.
Pour 2 tablespoons coconut flour in a bowl; cut 1/4 cup cold unsalted butter into flour until mixture resembles coarse crumbs. Stir walnut mixture into butter mixture.
Stir pears, apples, and lemon juice together in a bowl.
Beat 1/2 cup softened unsalted butter, 1/4 cup honey, and eggs together in a bowl. Whisk coconut flour, coconut milk, arrowroot powder, vanilla extract, baking powder, baking soda, and sea salt into egg mixture until a smooth batter.
Pour 1/2 the batter into the springform pan. Spread pears and apples in a layer over the batter. Pour remaining 1/2 the batter over apples and pears; top with walnut mixture.
Bake in the preheated oven until a toothpick inserted in the center of the cake comes out clean, 50 to 55 minutes. Cool for 10 minutes before running a butter knife around the edge of the cake and loosening the springform. Cool for 1 hour.