Butter a microwave-safe ring tin. Mix together pecans, 3/4 cup sugar and ground cinnamon. Sprinkle bottom and sides of the ring tin with 1/4 of the above mixture.
In a mixing bowl combine cake mix, pudding mix, 4 eggs, sour cream, vegetable oil and vanilla. Alternate layers of batter and crumb mixture in the greased tin.
Cook in microwave oven 5 minutes on low. Turn cake around if not on turntable. Bake 12 minutes on high, turning cake 1/4 turn every 4 minutes. Cool 18 minutes before turning out onto a cake plate. Baking time may vary depending on the wattage of the microwave. To test for doneness, press lightly on top of cake and if it springs back it is done. Sometimes the very top of the cake will remain moist, don't keep baking it until it is dry because the cake will be too done. Enjoy!