Heat your oven to 350 F and place a rack in the middle. Line 8 wells of a muffin pan with papers and set aside - OR - grease and flour an 8" cake pan.

Put the pistachios in a mini chopper and pulse until very finely ground. Be careful not to turn it into a paste! Transfer the ground nuts into a small bowl and set aside 2 tablespoons for topping the cupcakes.

Sift the flour, baking powder, salt, and cardamom into a medium bowl and set aside.

Add the butter and sugar to the bowl of a stand mixer fitted with the paddle attachment and cream on medium speed until very light and fluffy, about three minutes.

Scrape down the sides of the bowl, add the egg, and beat on medium speed until the mixture is uniformly smooth, about 30 seconds.

Scrape down the sides of the bowl and add half of the flour mixture. Mix on low speed until just combined.

Scrape down the sides of the bowl. Add the milk, vanilla extract, and almond extract and mix on medium-low speed until the mixture is uniformly smooth, about 15 seconds.

Scrape down the sides of the bowl and add the remaining flour mixture. Mix on low speed until barely combined - it's ok if there is still some flour on the sides of the bowl.

Remove the bowl from the mixer. Add the ground pistachios (except for the reserved 2 tablespoons) and mix gently to combine.

Divide the batter among the lined muffin cups (or pour it all into a cake pan). Bake until the tops spring back lightly when pressed and a toothpick comes out clean, about 16 minutes. (An 8" layer will take 22-25 minutes.)

Cool the cupcakes in the pan set on a rack for 10 minutes, then transfer to the rack to cool completely. (Similarly for the cake, let it cool in the pan for 20 minutes, then flip it out onto a rack to cool completely.)

Bring 1-2" of water to a simmer in a saucepan that is wide enough for the bowl of your mixer to sit on top of it (but not so big that the bowl falls in).

Add the egg whites and sugar to the mixer bowl. Whisk well to combine, then place over the pot of simmering water. Whisk constantly until the sugar has dissolved and the mixture is opaque and thick, about 3 minutes.

Transfer the bowl to the mixer and attach the whisk attachment. Start on low speed and over the course of 30 seconds, bring the speed up to high. Whip on high speed until the whites are thick and glossy and the bowl is cool to the touch, about 7 minutes.

While the whites are whipping, cut the butter into tablespoon-sized chunks. It's important that the butter is not too warm, so if it's squishy, put it in the fridge for a while so that it's somewhat firm but still pliant.

When the whites are cool, scrape down the sides of the bowl and lower the speed to 8. Add 2 tablespoons of the butter and whip until combined, about 10 seconds. Continue with the remaining butter, waiting 10 seconds between each addition.

When all the butter has been added, turn the speed to high and whip until the mixture comes together to form a thick frosting. This may take a while depending on how hot or humid it is, but don't lose faith - it will come together! After the frosting comes together, continue to mix on medium-high speed for another minute.

Scrape down the sides of the bowl, then add the rosewater and pink food coloring (if using) and whip on high speed for 10 seconds to combine.

Scrape down the sides of the bowl and transfer the frosting to a piping bag fitted with a large star tip.

Pipe the frosting onto the cupcakes once they are completely cooled and top each one with a sprinkling of ground pistachios and a rosebud (if using).