Basic fruit mixture
Combine the ingredients for the basic fruit mixture in a large bowl.
Preheat oven to slow (140-150deg C, gas mark 1-2); line base and sides of deep 22cm-square cake tin with one thickness brown paper and two thicknesses baking paper, extending papers 5cm above sides of pan.
Add butter and eggs to fruit mixture and stir well: add half the flour, well sifted and stir into mixture; add the remaining flour, well sifted, and stir into mixture.
Spread mixture into prepared cake tin; level top with spatula. Bake, uncovered, in slow oven about three hours.
Remove cake from oven; while still hot, brush with liqueur; cover cake with foil and allow to cool in tin overnight.