Grease a muffin pan and preheat your oven to 400°F. You can use any muffin pan for this recipe, but this is how I use my cast iron muffin pans. To prep them, I put a dab of oil or butter in each cup, then put the cast iron muffin pans in the oven to preheat while I make the batter. The combination of the melted butter and the hot iron will prevent sticking. Preheating the pan is not necessary with regular steel/aluminum muffin pans, but you should grease them. You can use paper liners, but I find that the muffins stick to them, which is annoying. Grease your muffin pan well, and you will have beautiful muffins that don't stick to the pan. Baking without a liner also gives the muffins a beautiful golden outside.

In the bowl of a stand mixer, cream together the butter and sugar until light and fluffy and almost white.

Scrape down the sides of the bowl, then add the eggs one at a time, beating well after each one.

Add the vanilla and yogurt or sour cream, and mix until incorporated.

Add the wheat flour, baking powder, baking soda, and salt to the wet ingredients all at once and mix on low speed just until smooth. Scrape the sides and bottom of the bowl to make sure the dry ingredients are fully incorporated and there are no dry spots left.

Fill each muffin cup 1/3 full with the muffin batter.

Drop one teaspoon of jam on top of the batter in each cup.

Then, add more tablespoons of batter until the muffin cup is about 2/3 full.

Sprinkle the top of the muffins with coarse sugar (optional.) Bake 18-22 minutes, until golden brown.

Remove muffin pans from oven and allow to cool for 5 minutes. Resist the urge to remove the muffins from the pan right out of the oven. It will not go well. The muffins need to firm up first. However, waiting until they are completely cool to remove them is also not advised, since they will steam themselves and become rubbery. Set your timer for 5 minutes. After 5 minutes, flip them out of the pan by running a butter knife under any sticky areas, tilting the pan to a 45° angle, and carefully popping them out. Place on a wire rack to finish cooling.

To clean your cast iron muffin pan and keep it well-seasoned, scrub out any remaining muffin residue with a scrubber and a bit of water. You can use soap if necessary, just don't soak the pan underwater. Rinse well, then dry. Rub the entire pan with a paper towel soaked in oil. Bake in a 400°F oven for five minutes to re-season. This will keep your pan as non-stick as possible.

Keep cooled muffins in an airtight container at room temperature and eat within 2-3 days.