Cream together butter and sugar until light and fluffy.  Add eggs, one at a time, and mix well after each addition.  Mix in vanilla and almond extracts.  In a separate bowl, combine flour, baking soda, cream of tartar and salt.  Add, one third at a time, to butter mixture, mixing until blended after each addition.  Using a wooden spoon, mix in 1/2 cup rainbow sprinkles.  Refrigerate dough until chilled, or overnight.

Scoop dough with 1" cookie scoop and roll top and sides of cookies in rainbow sprinkles.  Dip the bottoms of the cookies into coarse white sugar, or Sugar in the Raw (available in the grocery store).

Place on a parchment-lined cookie sheet and press each cookie slightly, with the palm of your hand, to make it disc-shaped.

Bake at 375 degrees for 9 - 10 minutes, or until cookies appear set and very lightly golden on bottom.  Transfer to cooling rack.