Kanelimuffinit

Yes, the 2 tablespoons of yogurt are listed as an extra for moisture, so the batter still works without them. You can swap in the same amount of sour cream, quark, or a plain plant-based yogurt. If you leave it out entirely, expect a slightly drier, more classic muffin crumb.

That usually means the batter was too thin or the swirling went too far. The recipe layers 1 tablespoon of batter, 1 teaspoon of filling, then more batter on top, and asks for only a light swirl - dragging a skewer through more than once will pull the heavy sugar-butter mixture straight down. Keep the top layer of batter generous enough to cover the filling.

Let them cool completely, then keep them in an airtight container at room temperature; the oil and yogurt in the batter help them stay moist for a couple of days. Avoid the fridge, which dries them out faster. They also freeze well once cooled - reheat briefly in a warm oven to bring back the soft, freshly baked texture.

You can mix the cinnamon filling (sugar, cinnamon, melted butter) ahead and keep it covered; just stir it before using, as the butter will firm up. You can also combine the dry ingredients - flour, baking powder, salt - in one bowl in advance. Don't mix the full batter ahead, because the baking powder starts working as soon as it meets the wet ingredients.

Overmixing is the main culprit: the dry ingredients should be stirred into the wet mixture only briefly, until just combined, even if a few lumps remain. Longer stirring develops gluten in the all-purpose flour and gives a chewy, dense crumb. Overbaking has the same effect, so start the toothpick test at the 18-minute mark rather than waiting for 22.