I've always been more of a pie girl than a cake fanatic, but if I have to choose a cake, I'll go for carrot every time. In fact, my husband and I had a carrot cake for our wedding. But can I tell you a secret? I can't stand cream cheese frosting. It's almost always too thick, too cloying, too heavy, and it overruns the flavor of the cake.
So when I make a carrot cake, I like a frosting that's a bit lighter and harmonizes more with the cake -- but still has the creamy texture of a cream cheese frosting. In my household pastry cream is considered a major food group so I start with an eggy, custardy base like you might find inside a cream puff. If it were up to me, I'd stop right there, but a little butter helps stabilize it and makes it spreadable. Add the butter then whip it like Devo. It's a perfect compliment to carrot cake, but really it would go well with just about any fruity cake or white cake. And with its golden hue, it'll brighten up your dessert *and* your day.
In a medium mixing bowl, whisk together egg yolks, sugar and corn starch until well combined and frothy
In a saucepan over medium heat, heat the milk and lemon zest to just under boiling (200 degrees F if you have a thermometer). Slowly whisk in about 1/2 cup of the hot milk into the eggs. Then pour the eggs into the saucepan, whisking constantly. Keep the pan over medium heat (or medium low if your stovetop tends to run hot) and keep whisking until the temperature reaches 185 degrees F. (If you do not have a thermometer, you will see the mixture suddenly seize up into a paste).
Put the mixture in a bowl and cover with plastic wrap, pressing the plastic right onto the surface of the custard (this prevents a skin from forming). Refrigerate for at least 2 hours or until completely chilled.
Once the custard is cooled have your butter ready, put it in a large mixing bowl and start whipping it (ideally with a hand mixer or stand mixer -- you could do it by hand, but only if you have strong wrists!).
The butter should be soft, but not melted and cut into cubes of about a tablespoon each. Drop in one cube at a time and whip until incorporated, then add the next cube. Once you have a whipped in all the butter, add the lemon juice and a pinch of salt and whip to combine.