Pre-heat oven to 375 degrees
In a large bowl, whisk flour, baking powder, cornstarch, cream of tartar and salt.
In a stand mixer, cream butter, and sugar until light and fluffy
Beat in the egg, almond, and vanilla extract until fully combined
Gradually add flour mixture until well blended
Using a medium-sized cookie scoop, drop the cookie dough onto a well-greased baking pan or parchment paper.
Using the palm of your hand, flatten the cookie dough about half way so it has a smooth surface. Don't press too hard or it will be thin and brown when it bakes.
Bake for 10 minutes. You want to remove them from the oven when they feel undercooked. You don't want them to get brown or crisp around the edges.
Place on a wire rack until thoroughly cooled
If using chocolate chips, place them in a small bowl and microwave in 30 second increments stirring in between each one. If using melting chocolate, melt according to the package.
Dip half of each cookie into the chocolate, shaking off any excess, and then using your fingers to sprinkle the rainbow sprinkles over the chocolate.