Melt the butter completely in the microwave or in a small saucepan over low heat;
Mix these ingredients in order: softened butter, eggs, sugar, and the room-temperature milk with a hand mixer on medium until the batter is light and fluffy;
Whisk together the flour, vanilla extract, and baking powder and add to the butter mixture;
Add the cranberries and apples. The batter should be quite liquid;
Divide it among the muffin pans, filling only 2/3 way up;
Add a few chopped nuts to the tops of the muffins before baking;
Bake in pre-heated static oven at 350°F (180°C) for 20 minutes. Do not open the oven until the end;
Then switch off the oven and open the door; let them rest in the oven for 5 minutes;
Take them out and let them cool on a cooling rack;
Combine them with some fruit and hot drinks for a delicious start of the day.