Preheat oven to 350°. Beat eggs about 7 minutes, or until light in color. Add brown sugar and beat 7 minutes longer. Stir in vanilla extract. Combine flour, baking powder and pecans; add to egg mixture. Pour batter into 2 (9-inch) round pans which have been greased and lined with greased waxed paper. Bake 30 minutes, or until cake tester comes out clean. Cool about 15 minutes in pans. Cake will fall slightly as it cools.
Invert one layer onto a flat serving plate. Remove waxed paper. Invert the other onto a wire rack. Remove waxed paper. You need to get this layer right side up. The best way to do this is to place the flat surface of its cake pan on top of the cake. Carefully invert pan, cake and rack in one motion and remove rack. Cake is now right side up on the bottom of the empty cake pan. Cool completely.
To make frosting, soften gelatin in water; add to coffee and bring to a full boil over low heat, stirring constantly. Remove from heat and add sugar, stirring to dissolve. Cool mixture about 30 minutes, or until it resembles thick syrup. Do not allow to jell. Whip the cream and gently beat syrup into the whipped cream until combined. Spread frosting over cake layer on plate. Carefully slide other layer off inverted cake pan to cover bottom layer. Frost top and sides of cake. Chill 12 hours before serving. This cake is well worth the effort!