Roast the garlic and cook bacon: Preheat oven to 400°F. Slice about ¼ inch off the top of a whole head of garlic to expose the cloves. Place in a small baking dish, drizzle with olive oil, and cover tightly with foil. Roast for 40–45 minutes, until soft and golden. At the same time, place bacon slices on a rimmed baking sheet and cook along side the garlic until crisp, checking at the 10 minute mark (it will probably take closer to 15 minutes). Reduce oven to 375°f. Let cool slightly, then squeeze 4 cloves from their skins for the dip, reserve the rest for another use (See Notes for a fresh garlic shortcut)
Meanwhile, caramelize the onions: Melt butter and a bit of olive oil in a large skillet over medium-low heat. Add sliced onions and cook slowly, stirring occasionally, for about 45 minutes, until deeply golden, soft, and caramelized. Season with salt and pepper during cooking. Reduce heat as needed to prevent burning. Don't rush this step.
Once the onions are caramelized, stir in the mashed roasted garlic, cayenne, smoked paprika, a pinch of nutmeg and chopped sage. Reduce heat to low. Cut the softened cream cheese into small pieces and add to the onions, stirring until smooth and evenly combined.
Add pumpkin and lemon juice until thoroughly combined.
Remove from heat and stir in chopped, cooked bacon and grated cheese, reserving a little bit of each for topping. Taste and adjust salt and pepper as needed.
Spoon mixture into prepared bread bowl and place on a rimmed baking sheet. Sprinkle reserved cheese and bacon on top. Tent loosely with foil and bake 30 minutes. Remove foil and bake another 15 minutes, until heated through and golden on top.
Serve warm with toasted bread, crackers, celery or red bell pepper strips.