In a large mixing bowl, beat together the butter and sugar until light and fluffy. Add egg and extracts and beat for 2-3 minutes, until combined and smooth.
In a small bowl, sift or whisk together the flour, salt and baking powder. Add to the mixing bowl and beat just until completely combined.
Pour the rainbow sprinkles into a bowl or on a plate. Roll about a tablespoon of dough into a ball then roll through the sprinkles. Place on a cookie sheet and repeat until done.
Bake at 350 degrees for 10-15 minutes. Cool on a wire rack.
I was able to get 2 dozen cookies and I began running low on the sprinkles for the last few cookies. If you like lots of sprinkles, you may want to have a second jar on hand just in case!