In a heavy-bottomed saucepan, heat oil and sauté all the onions over medium heat, stirring occasionally, until golden and semi-caramelized, about 15 minutes. 

Add peppers and continue to sauté, until vegetables are softened. Add one to two tablespoons of water, as needed, so onions don’t burn. 

Remove from heat, and season with salt to taste. Add cranberry sauce, stirring to combine. Serve warm or cold.