Preheat the oven to 350 degrees F (175 degrees C). Grease a loaf pan.
Place stuffing mix in a food processor and blend until fine; transfer to a large bowl.
Heat olive oil in a skillet over medium heat. Add celery; cook and stir until translucent, 5 to 7 minutes. Transfer to the bowl with the stuffing mix. Add eggs, milk, green onions, and lemon juice; mix well. Stir in salmon. Pour mixture into the prepared loaf pan.
Bake in the preheated oven until set and starting to brown on top, about 20 minutes. Sprinkle Cheddar cheese over loaf and bake until melted, about 10 minutes more.