Preheat and prepare your tin. Set the oven to 180°C (160°C fan) and grease a 23cm round springform cake tin. Line the base with a circle of parchment paper. This ensures the cake releases cleanly once baked.

Whisk the dry ingredients. In a large bowl, combine the flour, baking powder, bicarbonate of soda, cinnamon, nutmeg and salt. Whisk them together until evenly distributed — the spices will smell fragrant and the mixture will look a pale, sandy colour.

Cream the butter and sugars. In a separate large bowl, beat the softened butter, caster sugar and light brown sugar using a stand mixer or hand mixer on medium speed for about 3 minutes. The mixture should become pale, fluffy, and slightly grainy in texture.

Add the wet ingredients. Beat in the eggs one at a time, followed by the vanilla extract. The batter will look smooth and glossy at this stage. With the mixer on low, pour in the oil and buttermilk in a steady stream. The mixture may look a little separated — that’s perfectly fine.

Fold in the dry ingredients and apples. Add the flour mixture to the wet ingredients in two additions, folding gently with a spatula until just combined. You should see no streaks of flour. Fold in the chopped apples — the batter will feel quite thick and studded with apple pieces. Scrape it into the prepared tin and level the surface with the back of a spoon.

Bake until golden and risen. Place the tin in the centre of the oven and bake for 40–45 minutes. The cake is ready when a skewer inserted into the centre comes out clean with just a few moist crumbs attached, and the top is a deep golden brown. The edges will have pulled slightly away from the tin. Cool the cake in its tin for 15 minutes, then turn it out onto a wire rack to cool completely.

Make the salted caramel sauce. While the cake cools, place the butter and brown sugar for the sauce in a small saucepan over medium heat. Stir gently until the butter melts and the sugar dissolves — the mixture will bubble steadily and smell deeply of toffee. Once it’s completely smooth, about 3 minutes, remove from the heat and carefully stir in the double cream and the flaky sea salt. The sauce will be hot, glossy, and a warm amber colour. Let it cool for 10 minutes; it will thicken slightly as it sits.

Glaze and finish the cake. Place the cooled cake on your serving plate. Slowly pour the salted caramel over the top, letting it drip down the sides. Finish with an extra pinch of flaky sea salt scattered over the surface. Let the glaze set for at least 20 minutes before slicing.