01 - Combine rolled oats and milk in a medium saucepan. Bring to a gentle simmer over medium heat, stirring frequently to prevent sticking.
02 - Add orange zest, orange juice, grapefruit juice, and lemon zest. Continue cooking for 8–10 minutes, stirring continuously, until oats are creamy and have absorbed most of the liquid.
03 - Stir in honey or maple syrup. Adjust sweetness according to preference and remove from heat.
04 - Divide porridge evenly between two bowls. Top each serving with fresh orange slices, grapefruit segments, pistachios, and cranberries as desired. Serve warm.