First, go ahead and preheat your oven to 350°F (175°C). Prepare your loaf pan by greasing it well and dusting it lightly with flour or you can line it with parchment paper to make it easier to remove the cake later.
Next, grab a medium bowl and whisk together your dry ingredients: flour, baking powder, salt, and cinnamon. This helps spread the spices and leavening evenly throughout the batter.
Now, in a bigger bowl, beat the eggs and sugar until the mixture becomes light and fluffy. Slowly add the melted butter (make sure it’s cooled down), vanilla, orange zest, heavy cream, milk, and a good splash of dark rum. Mix everything until it’s well combined, but be careful not to overdo it here.
Gently fold the dry ingredients into the wet mix using a spatula. Just mix until you don’t see any streaks of flour over mixing can make your cake dense, and we want it nice and tender.
Pour the batter into your prepared pan, smoothing out the top with your spatula. Pop it in the oven and bake for about 50 to 60 minutes. To check if it’s done, insert a toothpick in the center it should come out clean or with just a few moist crumbs.
While the cake is baking, whisk together the powdered sugar, melted butter, and dark rum in a small bowl to make the glaze. Adjust the amount of rum so the glaze is smooth but still pourable.
When the cake comes out of the oven, and it’s still warm, poke holes all over the top with a skewer or fork. Slowly drizzle the rum glaze over the cake, letting it soak in beautifully. Let the cake cool completely in the pan on a wire rack before slicing and serving.