Sieve flour, baking powder and salt. Add butter to milk and keep hot. Beat eggs until thick. Gradually add sugar and continue beating for 5 minutes at medium speed. Quickly stir in sieved ingredients. Stir till blended; add hot milk mixture and vanilla essence. Blend thoroughly and pour into a paper - lined round baking pan at 350 * F or 180 * C for 25 -30 minutes. Cool for a while before turning onto wire rack.