Cream shortening, butter, and sugar together with an electric mixer until light and fluffy. Add eggs one at a time and mix until combined. Add the vanilla and combine. Mix the cream of tartar, baking soda, and flour in a separate bowl. Add the dry mixture to the sugar mixture alternating the flour and sour cream, beginning and ending with flour, in about 3 additions. Drop by rounded teaspoons (I use a small cookie scoop) onto a parchment lined baking sheet. Sprinkle each cookie lightly with sugar and press a raisin in the center. Bake at 350 degrees for about 12-13 minutes or until the cookies barely turn golden around the edges. Do not overbake. Note: If you don't have parchment paper or a Silpat mat, be certain to lightly grease the baking sheet with vegetable shortening.
Recipe by Baking and Eggs at https://bakingandeggs.com/2016/07/17/soft-amish-sugar-cookies/