Using an electric mixer on high speed (use whisk attachment if working with a stand mixer), beat eggs, lemon zest, and 1 cup plus 2 Tbsp. sugar in a large bowl until mixture is very light, thick, pale, and falls off the whisk or beaters in a slowly dissolving ribbon, about 3 minutes if using a stand mixer and about 5 minutes if using a hand mixer. With mixer still on high speed, gradually stream in 1¼ cups oil and beat until incorporated and mixture is even thicker. Reduce mixer speed to low and add dry ingredients in 3 additions, alternating with amaretto mixture in 2 additions, beginning and ending with dry ingredients. Fold batter several times with a large rubber spatula, making sure to scrape the bottom and sides of bowl. Scrape batter into prepared pan, smooth top, and sprinkle with more sugar.