Slice the jalapeno in half and remove the ribs and seeds.  Finely chop the tomato, onion, jalapeno, and cilantro.  Put the tomato, onion, jalapeno, cilantro, salt, garlic powder, cumin, and juice from the lime in a bowl and mix well.  Halve, seed, and scoop the meat from the avocado.  Put the avocado meat in a molcajete or bowl and mash it.  It should be smooth with small chunks.  Put the mashed avocado in the bowl with the everything else and mix well.  Serve with tortilla chips and margaritas.