Heat your oven to 325°F (163°C). Coat a loaf pan well with butter and flour, or line a loaf pan with parchment paper. Since this cake is rich, a well-prepped pan will make sure it slips out easily once baked.

In a large bowl, beat the butter and sugar together using a hand or stand mixer. Mix on medium speed for about 4–5 minutes until the mixture looks pale and fluffy. Scrape the bowl a couple of times so everything blends evenly.

Add the eggs one at a time, beating after each one goes in. This slow step helps create a smooth, glossy batter and keeps it from separating.

Mix in the vanilla, butter, and rum extracts. Once combined, add the sour cream and stir until smooth. The batter might look a little uneven at this point, but that’s nothing to worry about.

In another bowl, sift the cake flour with the baking soda. Gently add this mixture to the wet ingredients, mixing on low just until combined. Stop as soon as you no longer see streaks of flour—overmixing can make the cake heavy.

Pour the batter into your pan and smooth out the top. Give the pan a light tap on the counter to release air bubbles. Bake for 60–70 minutes, checking around the 55-minute mark. The cake is done when a toothpick inserted in the middle comes out clean.

As the cake cools, prepare the glaze. In a saucepan over medium heat, melt the sugar, stirring constantly until it turns a deep amber color. Carefully add the butter—it will bubble up—then stir until melted. Slowly whisk in the cream, followed by the salt. Let it cook for another minute, then remove from the heat to cool slightly.

Let the cake rest in the pan for about 10 minutes, then carefully turn it out onto a rack. While still warm, pour the caramel glaze generously over the top and sprinkle with flaky sea salt. Allow it to cool completely before cutting.