Preheat your oven to 375 degrees Fahrenheit (190 degrees Celsius).
Grease a 12-cup muffin tin(I love this one because it's stainless steel), or line it with paper liners. In a medium bowl, sift together the Einkorn flour, baking powder, and salt. If you don’t have a sifter, add them to the bowl and whisk them together. Set aside.
In a large bowl, use an electric mixer to cream the room-temperature butter and sugar until light and fluffy, about 3-4 minutes.This is the only step you will use a mixer for! Add the eggs one at a time, beating well with a wooden spoon after each addition. You can also use your favorite hand mixer tool—this is my favorite. Stir in the vanilla extract, milk, and lemon zest (if using).
Gradually add the flour mixture to the wet ingredients. Stir just until the ingredients are combined; be careful not to overmix.Overmixing is the number one cause of Einkorn recipes collapsing when baking. Gently fold the blueberries into the batter. Coating frozen or dehydrated berries with a little flour before folding them in will prevent sinking. Spoon the batter into the prepared muffin cups, dividing it equally between them. Each cup should be about three-quarters full.
Bake in the preheated oven for 20-25.
Begin checking your muffins at 20 minutes. A toothpick inserted into the center should come out clean or with just a few moist crumbs attached, signaling they’re done.
Let the muffins cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely. We never wait for them to cool completely before enjoying them!