In a large bowl, whisk the eggs until pale yellow and frothy. Briefly set aside.
Heat the olive oil in a large nonstick skillet over medium heat. When the oil is hot and shimmering, add the chicken sausage and onion to the pan and cook for about 5 minutes, or until the onions are translucent and the sausage is lightly browned. Add the chili powder and cumin and cook for 1 minute, just to toast the spices. Transfer to a bowl.
Wipe out the skillet and return it to the stove over medium heat. Pour in the eggs, and cook, stirring in large sweeping motions, until the eggs are just set (about 2 minutes). Immediately transfer to a plate.
Warm the tortillas. You can either wrap 4 tortillas at a time in a damp paper towel and microwave in 15-second increments until warmed through, or heat each tortilla right on your stovetop burner for 5 to 10 seconds per side.
Assemble your tacos! Each tortilla gets a scrambled egg topped with a heaping tablespoon of the sausage and onion mixture. Garnish with tomatoes, avocado, cilantro and hot sauce.