Line muffin pan with liners. I recommend parchment paper liners to prevent sticking. See my note below.
Preheat oven to 400° F.
Fluff the flour in it's container. Spoon it into a measuring cup (make sure you are using measuring cups for dry ingredients, without spouts). Place in a large mixing bowl.
Add baking powder, soda, sugar and salt.
Add cranberries (reserve some to place on top of muffins) and toss. This will prevent them from sinking to the bottom.
If using homemade buttermilk, whisk vinegar and half and half in a measuring cup. Let it sit for 5 minutes.
Whisk buttermilk, vanilla, egg and oil in a glass measuring cup or a small bowl.
Add to flour mixture and stir with a wooden spoon or spatula. Do not overmix.
Using an ice cream scoop, fill the muffin pan with batter. Add a few berries on top of each muffin, if desired.
Bake in 400° F for 7 minutes, then without opening the oven door, lower the temperature to 375° F and bake the muffins for 13 to 15 minutes more.
Mix powdered sugar with milk or lemon juice in a small bowl.
Cool muffins for 10 to 15 minutes, then glaze.
Notes
Use parchment paper liners. The store-brand cupcake liners tend to stick. You can also cut up parchment paper into squares for the bakery look.
Use buttermilk. You can easily make your own version with apple cider vinegar (or lemon juice) and half and half (or whole milk). It will produce a tender crumb and the muffins will be soft and fluffy! I recommend my recipe for Buttermilk Substitute.
To properly measure flour, fluff it in the container you store it in. Then spoon into the measuring cup and level off the top. Don't dunk the cup straight into the flour. You will end up with too much of it.
Please note, that the nutrition value can vary depending on what product you use. The information below is an estimate. Always use calorie counter you are familiar with.