12 tablespoons unsalted butter, softened, plus ½ tablespoon for glaze, and more for greasing pan
150 grams granulated sugar (3/4 cup)
2 teaspoons grated lime zest
½ teaspoon grated orange zest
3 large eggs, at room temperature
2 tablespoons fresh orange juice
190 grams all-purpose flour (1½ cups)
7 grams baking powder (1½ teaspoons)
3 grams fine sea salt (3/4 teaspoon)
30 grams confectioners’ sugar (4 tablespoons)
Heat oven to 350 degrees F. Coarsely chop any extra-large chunks of peel in the marmalade. (I did this by running a sharp knife through the marmalade in the measuring cup) Grease a 9-by-5-inch loaf pan, or a 9-inch round pan.
In the bowl of an electric mixer, beat together softened butter, sugar, lime zest and orange zest until light and fluffy, about 5 minutes. Beat in eggs, one at a time, until incorporated. Beat in ⅓ cup marmalade and the orange juice.
In a separate bowl, whisk together flour, baking powder and salt. Fold dry ingredients into wet until just combined.
Scrape batter into prepared pan. Bake until surface of cake is golden brown and a toothpick inserted in the centre emerges clean, 50 to 55 minutes (or less if you use a 9-inch pan). Remove from oven and transfer pan to a wire rack. Cool 10 minutes; turn cake out of pan and place on rack right-side up. Place a rimmed baking sheet under rack to catch the glaze.
Heat remaining ⅓ cup marmalade in a small pot over low heat until melted, adding a couple of drops of water if it seems overly stiff; whisk in confectioners’ sugar and ½ tablespoon butter until smooth. Slather warm glaze over top of cake, allowing some to drizzle down the sides. Cool completely before slicing.