Preheat the oven and prepare the pan. Arrange an oven rack in the middle position and preheat the oven to 350°F. Coat the bottom and sides of the loaf pan with coconut oil. Line the bottom and sides with parchment paper, leaving an overhang of an inch or two on each side, and set the pan aside.

Mix the almond butter swirl. In a small bowl, stir together 3 tablespoons of the almond butter, 1 tablespoon of the sugar, and 1 teaspoon of coconut oil until smooth. Set the almond butter mixture aside.

Mix the dry ingredients. In a large bowl, whisk together the flour, baking powder, salt, baking soda, and cardamom. Set aside.

Mix the wet ingredients. In a medium bowl, whisk the eggs to break up the yolks and whites. Add the remaining ½ cup sugar (4.6 oz / 130g) and whisk vigorously until the mixture is smooth and slightly thickened, about 30 seconds. Add the mashed banana, Greek yogurt, vanilla, remaining ½ cup almond butter (2.9 oz / 83g), and ½ cup coconut oil (3.9 oz / 110g) and whisk vigorously until the mixture is smooth (some banana lumps are okay).

Mix the wet ingredients into the dry. Pour the banana mixture into the bowl with the flour mixture and whisk gently just until you have a smooth batter with no dry spots. Add the almonds (if using) and fold the batter with a flexible spatula, scraping the bottom and sides of the bowl to make sure everything is well incorporated.

Fill the pan and make the swirl topping. Scrape the batter into the prepared pan and smooth the top. Dollop teaspoons of the reserved almond butter mixture all across the top of the batter and then use a toothpick or the tip of a paring knife to drag figure eights across the surface, making a swirl pattern.