Put 500 ml of warm water into a bowl, dissolve yeast and honey in it. Mix buckwheat flour, rice flour, pumpkin seeds, linseed and salt. Add the flour mixture to the yeast water and knead with the kneading hooks of the hand mixer. Add 2 tablespoons oil and vinegar and knead again.
Pour the soft dough into a box form (approx. 30 cm long) greased with oil. Smooth the surface and cut the dough lengthwise in the middle with a knife. Cover the dough and leave to rise in a warm place for about 1 hour.
Spread the dough with 2 tablespoons of oil. Fill an ovenproof container with water and place in the preheated oven (electric cooker: 225 °C/ circulating air: 200 °C/ gas: see manufacturer), place the box form on the oven rack. Bake bread for about 10 minutes. Reduce oven temperature (electric oven: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) and bake bread for another 50 minutes. Remove bread from the oven, let it cool down and turn out of the mould.