Mix dry ingredients together and set aside.
In a large bowl combine sugar, butter, eggs, and vanilla. Mix well.
Once incorporated, mix in orange zest, sour cream/or yogurt, and milk.
Then slowly add dry mixture to wet, mixing well. Use a whisk if needed to get out any clumps.
Carefully cut the raspberries in half. You won’t want them too big in the muffins.
In a separate bowl, mix halved raspberries with ¼ cup of flour. Just sprinkle the flour lightly over the raspberries, and turn gently with a spoon, so you don't crush the berries. Mixing the flour with the raspberries will keep them from all sinking to the bottom of your muffins.
Once all raspberries are coated, carefully fold raspberries into muffin mixture.
Once mixed, use a large kitchen scoop or spoon to spoon batter into prepared muffin tins. Fill about ¾ full.
Sprinkle 1-2 tablespoons of crumb topping over each muffin. Bake in preheated oven for 20-25 minutes until tops spring back and/or until a toothpick inserted comes out clean.
Let muffins rest in tin for 10-15 minutes after you remove them from the oven. The berries will be very hot and this will give the muffins time to rest.
You can top with extra orange zest if desired.
Once slightly cooled, remove from tin and enjoy!