For the bread:

1. Preheat oven at 350F. Butter a loaf pan and line it with parchment paper.
2. Cream eggs and sugar well. Add in kefir, oil, lemon zest and lemon juice.
3. Sift the flour into a bowl. Add it with baking powder into the wet mixture and mix just until combined.
4. Pour the batter in the prepared pan. Bake about 50 minutes or until a toothpick inserted comes out clean.
5. Let it cool before removing from the pan and slice.
6. Serve with extra lemon zest or lemon jam and rosemary.

For the lemon jam:

1. Slice the lemon zest thinly(mostly without the white parts), put them in a small pan, add sugar and water in it.
2. Heat it over medium heat stirring occasionaly until the sugar melts. Let it simmer until thickens.
3. Then you can take it from heat and garnish your cake.