Lightly grease a ½ sheet pan and preheat the convection oven to 325 degrees. Slice or split each Bridgford Biscuit in half horizontally, then place the top and bottom halves back together and arrange them on the prepared sheet pan. Heat the biscuits for 7 to 10 minutes, or until golden brown. Remove from the oven and lightly brush the tops with melted butter. Separate the biscuit halves, then layer the bottom halves with fresh avocado slices, tomato slices, spinach leaves, and red onion. Replace the biscuit tops and serve.