Preheat the oven to 350 degrees F (175 degrees C). Grease a loaf pan or wide casserole dish and sprinkle with breadcrumbs.
Beat eggs in a large bowl with an electric mixer until light and fluffy. Add sugar and beat in well. Stir in almonds and continue beating until batter is well combined. Add lemon juice, cinnamon, and rum, one after the other, beating until well combined. Pour batter into the prepared pan.
Bake in the preheated oven until a toothpick inserted into the center comes out with a few moist crumbs attached, 40 to 50 minutes. Cool on a wire rack for 5 minutes. Run a table knife around the edges to loosen. Invert carefully onto a serving plate or cooling rack. Let cool completely.
