In a deep skillet with a cover preheated over medium high heat, add oil, garlic, onion and jalapeno. Season with salt. Saute 2 minutes. Arrange mussels in the pan. Pour in beer and tomatoes and shake the pan to combine. Cover pan and cook 3 minutes or until mussels open. Remove from heat and spoon sauce down into shells. Garnish with parsley or cilantro. Serve immediately from the pan.