Preheat oven to 350°F. Place liners into muffin pans.
In a mixing bowl combine flour, cream of tartar, baking soda, and salt.
In a separate bowl mix sugar, oil, peanut butter, and vanilla; blend well.
In a small bowl whisk together the eggs; pour into the peanut butter mixture and blend well.
Add half the flour mixture and half the milk into the creamed mixture; gently mix. Add remaining flour and milk and mix again until blended; avoid over mixing.
Fill each muffin cup 1/4 way with batter. Add a dollop of jelly, then fill to 3/4 full with batter. Should make approximately 1 1/2 dozen muffins.
Bake for 20-25 minutes or until a toothpick inserted into the middle of one muffin comes out clean. Allow to cool for 5 minutes before serving.