Preheat the oven at 350 °F (180 °C). Butter and flour a loaf pan.
In the bowl of a stand mixer, beat the butter and zest on medium speed until light and fluffy, Add the sugar, eggs, coriander, and fennel and beat until smooth. Add half the milk and beat until just blended. Reduce the speed to low and add the flour and baking powder in two batches, scraping the sides in between the batches. Incorporate the remaining milk and the orange peel, once again beating until just blended.
Pour the batter into the loaf pan and smooth the top. Bake for 60 min, until a knife or wooden pick inserted in the middle of the cake comes out clean.
Let cool in the pan for at least 10 min before turning it out on a wire rack. Let cool fully to room temperature before serving thinly sliced.
Bake ahead and keep tightly wrapped for a week in the fridge, or 3 days at room temperature.
This classic tea bread can be served with jam, lemon curd, cream cheese, or ice cream.