Step 1

Preheat oven to 180C. Whisk oil, sugar, rind, juice and vanilla in an electric mixer until pale (3-4 minutes), then add egg yolks and whisk until fluffy (2-3 minutes). Sieve flours, ground spices, baking powder and bicarbonate of soda over, then add mixed seeds, caraway seeds and a pinch of salt, and stir to combine. Add beetroot and buttermilk, stir to combine and set aside.

Step 2

Whisk eggwhites and a pinch of salt in a bowl until firm peaks form, then fold into beetroot mixture. Spoon into a 22cm-diameter cake tin buttered and lined with baking paper, smooth top, and bake until risen and a skewer inserted withdraws clean (45-50 minutes). Cool in tin for 30 minutes, then cool completely on a wire rack.

Step 3

For crunchy seeds, dry-roast mixed seeds and caraway in a frying pan over medium-high heat until lightly toasted (1 minute), sieve icing sugar over and cook, stirring occasionally, until lightly glazed. Remove from heat, add rind, stir and cool on a piece of baking paper.

Step 4

For rapadura frosting, whisk ingredients in an electric mixer until thick (3-4 minutes), spread over cooled cake and serve scattered with crunchy seeds, topped with grated beetroot. Iced cake will keep in an airtight container for 2 days.