Generously grease and flour a 9-inch tube pan or two 8-inch loaf pans, tapping out any excess flour.
In the bowl of a stand mixer fitted with the paddle attachment, cream the sugar, softened butter, and vegetable shortening on medium-high speed for 5-7 minutes until the mixture is pale and fluffy.
Add the eggs one at a time, beating for 30 seconds after each addition and scraping down the sides of the bowl to ensure full incorporation.
Stir in the vanilla and lemon extracts.
In a separate bowl, whisk together the sifted flour, baking powder, and salt.
With the mixer on low speed, add the flour mixture to the creamed butter in three parts, alternating with the milk in two parts, beginning and ending with the flour. Mix only until just combined.
Pour the batter into the prepared pan and smooth the surface with an offset spatula.
Place the pan into a cold, unheated oven. Turn the oven on and set the temperature to 325°F (165°C).
Bake for 1 hour and 15 minutes to 1 hour and 25 minutes, or until a long wooden skewer inserted into the thickest part comes out clean.
Remove from the oven and allow the cake to cool in the pan for 15-20 minutes.
Carefully run a knife around the edges and center tube, then invert the cake onto a wire rack to cool completely before slicing.