Preheat the oven to 350F.

Line a 12-muffin tin with cupcake papers; set aside.

Using a sharp knife, carefully remove the peel and pith from both grapefruit.

Cut the segments out of each, discarding membranes and seeds and draining well; reserve juice.

Set aside 12 segments for garnish, and then chop remaining. (You should have about 1/2 cup juicy, chopped fruit.)

In a large bowl, whisk together eggnog, sugar, vanilla, eggs and 2 tablespoons of the reserved juice. (Save remaining for another use, or sip as a cook’s treat.)

Add flour, baking powder, nutmeg, baking soda and salt and whisk again, just until combined.

Fold in chopped grapefruit, and then spoon batter evenly into the prepared tin and top each muffin with a grapefruit segment.

Bake until golden brown and cooked through, about 25 minutes.

Serve warm or at room temperature.