Diamond Cardamom Sparkle Cookies

Name: Diamond Cardamom Sparkle Cookies
Ingredients: 1½ cups (300 g) granulated sugar; 1 cup (2 sticks) unsalted butter, room temperature; 1 large egg, room temperature; Zest of 1 lemon; 2¼ cups (281 g) all-purpose flour; ½ tsp. ground cinnamon; ¼ tsp. freshly grated nutmeg; 2 tsp. green cardamom seeds (crack pods and remove seeds if needed); 1 tsp. black peppercorns; ½ tsp. kosher salt; 1 lb. (453 g) powdered sugar; 3 Tbsp. light corn syrup; 5 Tbsp. fresh lemon juice; Teal gel food coloring (such as AmeriColor soft gel paste #110); ¼ cup salted roasted almonds, coarsely chopped; Edible gold metallic paint, well shaken (optional); Teal chunky sugar (such as Layer Cake Shop Teal Chunky Sugar; for decorating); Light blue chunky sugar (such as Layer Cake Shop Light Blue Chunky Sugar; for decorating); A 3½ diamond cookie cutter (optional)