Heat a medium saucepan over medium heat. Add the oil and swirl to coat the bottom of the pan.
Add the garlic and ginger and sauté until soft, about 3 minutes.
Add the mushrooms and cook for another 5-7 minutes.
In a medium bowl, combine the tomatoes, onions, mushrooms, jalapenos, cilantro and lemon juice.
Mix well and season to taste with the salt and pepper.
Place in the refrigerator, covered, until ready to use.