Prepare sauce first. In a saucepan, combine the first four ingredients. Bring to a boil over medium heat and cook, uncovered, for 5 minutes. Remove from heat; stir in vanilla and rum flavor.
For cake: Combine flour, sugar, baking powder, cinnamon and salt. Mix well.
Combine milk, melted butter, and vanilla flavor in a small bowl. Add all at once to the flour mixture; blend quickly.
Spread in a greased 12 x 18-inch steamtable pan. Then, pour the sauce over the top. Do not mix in. Scatter the pecans over the sauce.
Bake at 350°F for 40 to 45 minutes, or until the center bubbles up. Serve warm with ice cream or whipped cream.