Coffee cake is a versatile treat that is often enjoyed with coffee or tea. It is a simple and lightly sweet cake that is perfect for casual gatherings, brunches, or as a snack or dessert. Hazelnuts can be added to the coffee cake to add a nutty flavor and crunchy texture. The recipe includes ingredients such as flour, sugar, vanilla, eggs, butter, salt, baking powder, baking soda, Greek yogurt (or sour cream), almond meal, and milk. The cake is topped with a streusel mixture made from butter, brown sugar, cinnamon, flour, and hazelnuts. The cake should be baked at 325°F and cooled in the pan to retain moisture. Other nuts can be substituted for hazelnuts, such as walnuts, pecans, almonds, pistachios, or macadamia nuts, to add different flavors and textures to the cake.