Preheat oven to 160 degrees fan forced and place rack into middle of oven
Grease and flour a large Bundt tin (see notes), and place onto a baking sheet
Place butter and zest into TM bowl and mix 40 seconds / 50 degrees / speed 4 (this will loosen up the butter but not melt it completely which you don’t want to do … if it is completely melted the cake will be heavier)
Insert butterfly
Add buttermilk, orange juice, Grand Marnier and eggs and mix 10 seconds / speed 3
Add sugar, flour, baking powder and bi-carb soda … the bowl will be quite full so use a spatula to stir some of the liquid from the base to the top before continuing
Replace lid and mix 10 seconds / speed 3
Lift lid, stir around top of bowl and mix a further 30 seconds / speed 3
Pour batter evenly into Bundt tin and level top
Bake for 60 minutes, or until a skewer inserted comes out clean (it takes exactly 60 minutes in my oven)
Remove cake from oven and allow to rest in tin for 15 minutes
Turn the cake out onto a cake rack, placing the rack over a tray (to catch excess sauce when you drizzle it over the cake)
Make the sauce (see below for method)
Poke a few holes into the cake with a skewer
Brush some of the sauce over the cake covering the whole surface area … allow to set on cake for 5 minutes, then repeat brushing a second time, then pour balance of sauce over the top of the cake allowing the excess to drip into the tray underneath
Allow to cool before serving at room temperature
Keeps well for a few days