Heat oven to 350. Making sure all ingredients are at room temperature, grease two 9 inch round cake pans with 1 tablespoon unsalted butter, dust with 1-1/2 tablespoons flour, tap out excess and sit aside.
Sift flour, baking powder and salt together, set aside.
Beat remaining unsalted butter and 2-1/2 cups sugar in a bowl with an electric mixer until fluffy.
Add vanilla and eggs one at a time, beating after each addition.
Add flour mixture and milk alternately in 3 batches, beating smooth after each addition. Divide batter between pans.
Bake until golden, 30-35 minutes. Let cool on a rack for 10 minutes, remove cakes, let cool completely. Slice tops off cakes to level them.
To make icing, cook remaining sugar and salted butter in a pot over high heat, stirring constantly, until light golden 7-8 minutes.
Carefully stir in evaporated mil, reduce heat to medium low cook stirring constantly, until smooth, 8-10 minutes. Cook stirring occasionally until icing registers 240 on a candy thermometer about 1-1/2 hours.
Remove from heat, beat with a wooden spoon until thick, glossy and spreadable, 20-25 minutes. (A dollop on a plate should ooze only slightly.)
Ice bottom layer of cake, top with second layer and ice the outside. Chill cake until set.