Texas Sheet Cake With Chocolate Buttermilk Frosting

Texas Sheet Cake
Rich and fudge like. The ultimate Chocolate cake.

For the cake:
2cups flour
2cups sugar
1tsp.baking soda
1/4tsp.salt
1cup margarine
1/2cup  cocoa powder
2 eggs
1/2 cup buttermilk-( add 1tbl. white vinegar to a measuring cup then add the milk to the 1/2 cup mark. let stand 15 minutes, and you'll have buttermilk)
1-1/2 tsp. vanilla
Chocolate Buttermilk Frosting- recipe below

Instructions:
Heat oven to 350*
Grease a 15x10x1 or 13x9x2 baking pan
In a bowl whisk together, flour, sugar, salt, and baking soda.
In a saucepan mix butter cocoa, and 1 cup of water. stirring constantly, bring to boil. remove from heat.
Add the cocoa mix to the flour mix and beat on high until combined.Add eggs buttermilk and vanilla.
Beat on high for 1 minute, and pour batter into the baking pan.Bake about 30 minutes.
Pour warm frosting over warm cake and cool.

Chocolate Buttermilk Frosting:
 1/4 cup butter
 3tbl. cocoa powder
 3tbl. buttermilk
 2-1/4cups confectioners sugar
1/2tsp.vanilla
3/4 cup chopped pecans-optional
In a saucepan mix butter, cocoa powder and  buttermilk.bring to a boil.
Remove from heat and add confectioners sugar and vanilla. beat until smooth. stir in chopped pecans.
Pour over warm cake.