LAS VEGAS — Canelo Alvarez proved nothing more than easy money forFloyd Mayweather Jr. Mayweather turned one of the richest fights ever into just another $41.5 million payday Saturday night, dominating Alvarez from the opening bell and winning a majority decision in a masterful performance that left no doubt who the best fighter of his era is. Fighting off his shortest layoff in years, Mayweather was sharp, efficient and sometimes brutal in dismantling an unbeaten fighter who was bigger and was supposed to punch harder. He frustrated Alvarez early, pounded him with big right hands in the middle rounds, and made him look just like he said he would — like any other opponent.