Preheat the oven to 350 degrees F.

Line a muffin pan with 24 cupcake liners.

In a mixing bowl, combine the butter, sugar, and orange zest, beat using an electric mixer until fluffy.

Add in the eggs, beat again.

In a smaller bowl, combine the flour, baking powder and salt, gently mix with a spoon. Gradually add the flour mixture to the wet ingredients, mixing with a spatula.

Add in the poppy seeds, mix again by hand.

Bake for 15-18 minutes to until a toothpick inserted in the center of the cupcakes comes out clean.

Allow the cupcakes to cool for 5 minutes before removing them from the pan. Allow them to cool completely before frosting.

In a mixing bowl, combine the butter and vegetable shortening, beat using an electric mixer until fluffy.

Add in the fresh orange juice and zest, gently mix by hand with a spatula.

Begin to add the powdered sugar, about 2-3 cups at a time. Continue adding powdered sugar until the frosting no longer looks wet and tastes good to you.

Add a little bit of orange gel food coloring and mix one last time.

Transfer the buttercream into a piping bag fit with a Wilton 1M tip. Pipe buttercream swirls on each cupcake. Top each cupcake with an orange slice.