### Traditional Boston Baked Beans Recipe

#### Ingredients:
- **1 pound navy beans or pea beans** (soaked overnight and drained)
- **1/4 pound salt pork** (cut into 1/2-inch cubes)
- **1 medium onion** (peeled and whole)
- **1/3 cup molasses**
- **1/4 cup brown sugar**
- **1 teaspoon dry mustard**
- **1/2 teaspoon ground black pepper**
- **3 cups hot water**
- **1/4 cup apple cider vinegar** (optional for a slight tang)
- **Salt** (to taste)

#### Equipment:
- Bean pot or a heavy-bottomed oven-safe Dutch oven with a lid

#### Instructions:

1. **Prep the Beans:**
   - Rinse the soaked beans thoroughly and drain. Place them in a large pot, cover with water, and bring to a boil. Simmer for about 30 minutes until the beans are tender but not fully cooked. Drain and set aside.

2. **Prepare the Salt Pork:**
   - In your bean pot or Dutch oven, render the salt pork over medium heat until it begins to brown and release fat. Remove the pork pieces, leaving the fat in the pot.

3. **Layering Ingredients:**
   - Preheat your oven to 250°F (120°C).
   - In the pot with the pork fat, add the pre-cooked beans, salt pork pieces, whole onion, molasses, brown sugar, dry mustard, and black pepper. Stir to combine all the ingredients evenly.

4. **Cooking Liquid:**
   - Pour in the hot water (it should just cover the beans). If using, add the apple cider vinegar. Stir gently to mix through.

5. **Baking the Beans:**
   - Cover the pot with its lid and place it in the preheated oven. Bake for about 4-6 hours, checking occasionally. If the beans seem too dry during cooking, add a bit more hot water.

6. **Final Hour of Cooking:**
   - Remove the lid for the last hour of cooking to allow the sauce to thicken and the top to get a slight crust.

7. **Finishing Touches:**
   - Once the beans are tender and the sauce has thickened to your liking, remove the pot from the oven. Discard the whole onion. Taste and adjust the seasoning with salt and additional pepper if needed.

8. **Serving:**
   - Serve your Boston baked beans hot as a side dish, perhaps with cornbread, hot dogs, or grilled meats.

#### Notes:
- **Soaking the Beans:** Soaking the beans overnight helps reduce cooking time and improve their texture.
- **Adjusting Sweetness and Tanginess:** Depending on your preference, adjust the amount of molasses, brown sugar, and vinegar to strike the right balance of sweetness and tanginess.
- **Slow Cooker Variation:** If using a slow cooker, follow the same initial steps for soaking, boiling the beans, and rendering the salt pork. Combine all ingredients in the slow cooker and cook on low for 8-10 hours or on high for about 5-6 hours.

This traditional approach to Boston baked beans brings out the classic flavors and textures that make this dish a cherished part of New England cuisine. Enjoy the process and the delicious results!