Preheat your oven to 180 C/ 350 F. Butter and flour two 7 inch round pans , line the bottom with parchment paper.

In a mixing bowl , whisk together all the dry ingredients - flour , baking powder , baking soda , salt , zest , sugar .

In another bowl , whisk together the liquid ingredients - oil, milk , vanilla , lime juice, vinegar . Whisk in the vinegar in the end.

Pour the liquid ingredients into the dry and fold/whisk until flour cannot be seen. It will be a thick batter , slightly foamy.

Divide immediately into prepared pans and bake for 30-35 minutes until a toothpick inserted in centre , comes out clean.

Cool in pan for 10 minutes and then unmould to cool completely on a wire rack.

Puree the strawberries in your blender or food processor , and strain. You should have 1/2 cup puree.

Heat this puree in a saucepan on low , stirring occasionally. Continue until it is reduced to about 2 or 3 tablespoons. It should thick.

Beat the butter for a few minutes until pale.

Sift in the 2 cups of icing sugar, half cup at a time, beating for few minutes after each addition until smooth.

Add the thickened strawberry puree and beat until incorporated.

If your buttercream is too thin, add more sifted icing sugar a few tablespoons at a time.

If its too thick , add milk, one tablespoon at a time.

Beat until desired consistency is achieved.

Divide each cooled cake horizontally into two layers.

Spread 1/4 cup of buttercream on one layer, place another on top and repeat.

Using a spatula , cover the top and sides of the cake with the remaining buttercream.