Preheat your oven to 350 degrees.
To cook the ground beef: Using a large pan or skillet over medium high heat, heat the olive oil. Add in the lean ground beef and cook until completely browned through. Drain any fat if desired. Sprinkle the taco seasoning over the cooked ground beef and mix together. Taste. Feel free to add a couple tablespoons of water if the seasoning tastes too concentrated. Remove from heat and set aside.
Using a large baking sheet lined with parchment paper, lay down the tortilla chips in an even layer. Sprinkle on the seasoned, cooked ground beef and then the shredded cheese. At this point, you can also sprinkle on the diced tomatoes and bell peppers. Sometimes, I like to bake them in the oven over the nachos and sometimes I like to add the diced vegetables AFTER baking so they are still raw and add some crunch and texture.
*Bake in the oven for 18 to 20 minutes, or until the cheese is nice and melted. Remove from the oven and top with the diced tomatoes and bell peppers (if you didn't add them earlier). Garnish the nachos with the jalapeños, avocado cubes (or serve with guacamole) and green onions. Serve with salsa and sour cream if desired. Enjoy immediately!