Combine the oats and water; let stand for 15 minutes. Beat 1/2 cup butter with an electric mixer until creamy; gradually add 1 cup sugar and 1 cup brown sugar; beating well. Add the eggs, one at a time, beating after each addition.
Combine the flour, soda, and salt; add to butter mixture alternately with the oat mixture, beginning and ending with the flour mixture. Mix at low speed after each addition until blended. Stir in 3/4 cup pecans.
Pour into a greased and floured 13x9x2 inch pan. Bake at 325 degrees for 45 minutes or until a wooden pick inserted in the center comes out clean.
Combine 3/4 cup brown sugar and the remaining 3 ingredients; spoon evenly over the top of the cake. Broil 5 1/2 inches from heat (with electric door partially opened) 2 minutes or until bubbly. Cool in the pan on a wire rack.