Beat oil and sugar with egg with an electric mixer until smooth. Beat in vanilla, salt, and baking soda until well blended. Put milk and lemon juice together in cup until curdled and pour into batter, beating to blend well. Beat in cocoa powder and finally the flour, beating 3 minutes after last addition, scraping down sides and bottom of bowl often. Divide batter equally between dozen paper-lined cupcake wells. Bake ata 180ºC for 25 minutes or until a toothpick inserted comes out clean. Cool in pan on rack 20 minutese. Remove to platter to continue cooling. Frost as desired.