The butter and strawberries place in a small, round glass bowl. Warmed, until the butter is melted. Eggs, sugar, flour, baking powder and beat with a mixer. Pour the egg mixture over the heated strawberries. On top sprinkle with coarsely chopped walnuts. Gently mix. Bake 15-20 minutes in a moderate oven, checking with a skewer (when the environment becomes dry, the cake is baked). After cool down, the cake is removed from the vessel walls, and turns on a plateau.