Warm 1 tablespoon of the oil in a skillet set over medium heat. Add the onions and cook until golden, 6 to 8 minutes. Add a pinch of salt and the garlic and cook for another 3 minutes. Add the peas and cook for 1 minute. Remove from the heat and cool. Place the peas and onions in a food processor and add the dill, mint, lemon juice, the remaining 1 tablespoon oil and 1/4 cup water. Blend until smooth. Season with salt and pepper, then place in a bowl and serve.