Preheat the oven to 350° degrees Fahrenheit and set an oven rack in the middle position.
Grease a 12-cup bundt pan or 2 loaf pans with butter and dust with tapioca flour.
In a medium bowl, whisk together the flours, poppyseed, baking soda and salt. Set aside.
In the bowl of an electric mixer fitted with the paddle attachment cream butter (or coconut oil) and honey together. Scrape down the sides of the bowl, then beat in the eggs one at a time, beating well after each addition.
In a small bowl, combine the zest and juice of four lemons.
With the mixer on low speed, beat in 1/3 of the flour mixture, then 1/3 of the lemon mixture and combine well. Repeat with another third of the flour, then another third of the lemon mixture. Finally, beat in the remaining flour and lemon mixture. Scrape down the sides of the bowl and give another stir to make sure all ingredients are combined well.
Pour the batter into greased and floured pan(s) and smooth with a spatula.
Bake for approximately 50 minutes or until toothpick comes out clean.
Cool the cake in the pan for 15 minutes on a rack.
Invert the warm cake onto a cooling rack and allow to cool completely (approx.. 1 hour – don’t rush as the glaze will just melt straight into the cake if it’s too warm)
Mix all ingredients with a fork until smooth. Spoon the glaze over the top of the cake(s), letting it drizzle down the sides. Give a few minutes to set.