Make the muffins: In a large bowl, whisk together the eggs, ½ cup sugar, honey, mascarpone, lemon zest, lemon juice, lime zest, and lime juice until well combined.
Add the grapeseed oil and whisk until incorporated.
In a separate bowl, whisk together the flour and baking powder.
Fold the dry ingredients into the wet ingredients until just combined, being careful not to overmix.
Make the soaking syrup: In a small saucepan, combine the 2 tablespoons sugar, water, and 2 tablespoons lemon juice. Bring to a simmer, stirring occasionally, until the sugar has dissolved.
Divide the batter evenly among a 12-cup muffin tin lined with paper liners.
Bake at 400°F for 15-18 minutes, until a toothpick inserted in the center comes out clean.
While the muffins are still warm, use a toothpick or skewer to poke holes all over the tops of the muffins.
Spoon the soaking syrup over the muffins, allowing it to soak in.
Let the muffins cool completely before serving.
