Zest the lemons directly into the granulated sugar and set aside. The longer this sits, the more pronounced the lemon flavor will be.

In the bowl of a stand mixer fitted with the paddle attachment, combine the flour, lemon sugar, salt, and baking powder. Mix on low just to distribute.

Add the cold cubed butter and mix on low until fully incorporated and the mixture resembles coarse, damp sand with no visible butter pieces remaining. Run your hands through the bowl to check.

In a separate bowl, whisk the eggs and heavy cream until smooth. Add the lemon juice immediately before adding to the dough.

With the mixer on low, slowly pour in the cream mixture and mix until just incorporated. Do not overmix.

Scrape the dough onto plastic wrap, press into a disk, wrap tightly, and refrigerate for 2 hours.

Roll or press the dough to ½ inch thickness. For uniform scones, roll into a 6-inch square, divide into four 3-inch squares, and cut each diagonally into triangles. For rustic scones, press into a circle and cut 12 triangles. Place on a parchment-lined baking sheet, wrap in plastic wrap, and freeze for at least 1 hour or overnight.

Preheat the oven to 325°F convection or 350°F conventional.

Brush the frozen scones with heavy cream and sprinkle immediately with sparkling sugar, working 2 to 3 scones at a time so the cream does not freeze before the sugar goes on.

Bake for 20 to 25 minutes, starting to check at 20 minutes, until the edges are golden and the centers feel just set. Cool completely on the baking sheet.