Position a rack in the middle of the oven and preheat the oven to 375 degrees F.

Line twelve 1/2-cup muffin cups with paper liners.

Whisk together the flour, sugar, baking powder, salt, and nutmeg in a medium bowl.

In another bowl, whisk together the oil, milk, eggs, and vanilla.

Finely grate the zest from the oranges into the wet ingredients.

Create a small well in the center of the dry ingredients.

Pour the wet ingredients and raspberries into the center of the dry ingredients.

Stir the wet and dry ingredients together with a wooden spoon until the dry ingredients are moistened but still a bit lumpy.

Divide the batter evenly among the muffin liners.

Sprinkle the tops generously with sugar (about 1/2 teaspoon per muffin).

Bake until golden brown and a toothpick inserted in the centers comes out clean, about 25 to 30 minutes, rotating the pan halfway through cooking.

Cool muffins in the pan on a rack for 5 to 10 minutes.

Turn the muffins out of the pan and cool on the rack completely.

Serve warm or at room temperature.