In a large bowl, whisk to combine flour, baking powder and salt. In the bowl of a stand mixer, use a paddle attachment to beat butter and sugar on medium speed until pale and fluffy, about 2-3 minutes. Add eggs, one at a time, and beat to combine. Reduce speed to low and gradually beat in flour. Divide dough in half and shape each half into a flat disk.
Working one at a time, place the dough on a silpat or piece of parchment paper cut to 12x17 inches. Cover with a large piece of plastic wrap and roll dough out to 1/4-inch thick. Place rolled dough, covered with plastic on a baking sheet. Repeat process with 2nd disk and place rolled dough on top of 1st piece. Refrigerate until dough is firm, about 1 hour.
Preheat oven to 350 degrees F. Line 2 baking sheets with parchment paper. Remove plastic from dough and use a 4-inch cat emoji cutter to cut out shapes. Place cookies 1 1/2-2 inches apart on prepared baking sheets. Roll out scraps and repeat process. Chill for about 15 minutes if dough is too soft.
Bake cookies rotating baking sheets halfway through until edges start to turn golden, about 12-14 minutes. Transfer cookies to a wire rack to cool completely before decorating.
To make the icing: Place sugar, meringue powder and 1/2 cup water in a large mixing bowl. Using a hand-held mixer or stand mixer fitted with whisk attachment, whisk to combine until smooth and thick, adding additional water to achieve a thick but pourable consistency. Separate icing into four bowls and use coloring gels to dye icing red, yellow, black, and light blue.
Fill a small squeeze bottle with yellow royal icing and trim the tip to make it easier to squeeze the icing out. Alternatively use a pastry bag fitted with a small tip. Fill a pastry bag fitted with a small tip or squeeze bottle with black royal icing. Fill a pastry bag fitted with a small tip or small squeeze bottle with light blue royal icing.
To decorate cookies, start with the yellow royal icing and draw an outline around the edge of the cookie. Fill the center with yellow icing by squeezing in a zig zag and then use a toothpick to make smooth. Place heart eyes on some of the cookies. Let icing dry completely before decorating the face.
Once the yellow icing is dry, use the black icing to make eyes, whiskers and a mouth. Let dry completely.
Use the light blue royal icing to draw tears of laughter on some of the cat emojis.