Reverend Samuel Ruggles brought Arabica coffee cuttings from Brazil to the Kona coast of Hawaiʻi's Big Island in 1828. The volcanic western slopes of Mauna Loa and Hualalai, between 600 and 900 metres, proved unexpectedly ideal: mineral-rich basalt soil, warm mornings, and the trademark 'Kona snow' of afternoon cloud cover that shades the plants from harsh equatorial sun. Genuine 100% Kona coffee is among the world's most expensive, selling for $30–60 per pound at source. Its flavour profile is smooth, medium-bodied, low in bitterness, with notes of brown butter, hazelnut, and tropical fruit. Paired with the macadamia nut, itself an Australian import that became deeply embedded in Hawaiian agriculture, this coffee cake is an expression of Hawaiʻi's layered identity: Polynesian roots, American statehood, and a history of brought-in plants that became entirely its own.
Ingredients
Cake
120 ml strong brewed Kona coffee (or best-quality washed Arabica), cooled
240 g plain flour
150 g caster sugar
50 g light brown sugar
1.5 tsp baking powder
0.5 tsp fine salt
115 g unsalted butter, melted and cooled
2 eggs, large
120 g sour cream or plain yoghurt
1 tsp vanilla extract
Macadamia Streusel
80 g macadamia nuts, roughly chopped
60 g plain flour
60 g dark brown sugar
1 tsp ground cinnamon
55 g cold unsalted butter, cubed
Coffee Glaze
80 g icing sugar, sifted
2 tbsp strong brewed Kona coffee, cooled
Method
Preheat oven to 175°C (350°F). Grease and flour a 23cm (9-inch) round cake tin or a 20×20cm square tin.
Make the streusel: combine the flour, dark brown sugar, and cinnamon in a bowl. Rub in the cold butter with your fingertips until the mixture resembles coarse crumbs. Stir in the chopped macadamias. Refrigerate while you make the batter.
In a large bowl, whisk together the flour, caster sugar, light brown sugar, baking powder, and salt.
In a separate bowl, whisk together the melted butter, eggs, sour cream, cooled coffee, and vanilla until smooth and emulsified.
Pour the wet ingredients into the dry and fold gently with a spatula until just combined. Do not overmix; a few streaks of flour are fine at this stage.
Pour the batter into the prepared tin and spread level. Scatter the cold streusel evenly across the entire surface.
Bake for 40–45 minutes, until a skewer inserted in the centre comes out clean and the streusel is deep golden. Allow to cool in the tin for 15 minutes, then turn out onto a wire rack.
While the cake cools, make the glaze: whisk the sifted icing sugar with the coffee one tablespoon at a time until you have a thick, pourable glaze. Drizzle over the warm cake.
Serve at room temperature. The flavour deepens and the crumb tightens after a few hours; this cake is better the next day.
Notes
100% Kona coffee is expensive but the flavour difference is real; use it if the occasion calls for it. For an everyday version, a good Guatemalan Antigua or Colombian washed Arabica gives similar smoothness. Toasting the macadamias for 5 minutes at 160°C before chopping intensifies their buttery flavour significantly.
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