Line a plate with a paper towel. Arrange bacon on one prepared baking sheet and bake until bacon reaches desired crispness, 14-20 minutes. Transfer bacon to towel-lined plate to remove excess fat. While bacon bakes, stem, seed, and cut red bell pepper into 1/2" dice. Cut potato into 1/2" dice. Trim and thinly slice green onions on an angle, keeping white and green portions separate.

Heat a medium non-stick pan over medium-high heat. Add 2 tsp. olive oil, peppers, potatoes, 1/4 tsp. salt, and 1/4 tsp. pepper to hot pan and cook, stirring occasionally, until vegetables begin to brown, 4-7 minutes. Transfer vegetables to second prepared baking sheet and spread into a single layer. Roast until vegetables are brown and tender, 15-20 minutes. Reserve pan; no need to wipe clean. While vegetables cook, cook spinach.

Return pan used to cook potatoes to medium-high heat. Add 1 tsp. olive oil, white portions of green onions, spinach, and a pinch of salt to hot pan and cook until spinach is wilted and tender, 1-2 minutes. Remove spinach to a plate and blot dry with paper towels. Wipe pan clean.

Return pan used to cook spinach to medium-high heat. Add butter to hot pan and melt. Add liquid egg and a pinch of salt. Using a rubber spatula, constantly scrape along bottom of the pan until eggs are mostly set and top is still wet, 2-3 minutes.

Add spinach and goat cheese (breaking up with your hands if needed) to one side of eggs. Use a spatula to fold other half of eggs over spinach and cheese. Alternatively, slide filled side of omelette onto cutting board and use pan to flip remaining eggs to cover filling. Divide into two.

Place potatoes O'Brien on a plate and garnish with green portions of green onions. Place omelette on top of potatoes.