Prepare the bell peppers and set them aside.
In a large skillet, heat olive oil over medium high heat; add diced onions and cook for 2 minutes, or until translucent.
Stir in garlic and continue to cook for 30 seconds, or until fragrant.
Add ground pork to the skillet and break it up with a spatula or wooden spoon while it cooks.
Season with salt, pepper, and thyme; stir and continue to cook until browned on all sides, about 5 to 7 minutes. Carefully drain and discard grease.
Set skillet over heat and mix in the tomato paste.
Stir in diced tomatoes and rice; cook for 2 more minutes, or just until heated through.
Remove from heat and stuff each bell pepper with ground meat mixture.
Arrange stuffed bell peppers in the crock pot.
Place the reserved tops back onto each bell pepper.
Pour water around the base of the peppers.
Cover and cook on LOW for 6 to 7 hours or on HIGH for about 4 hours.
Serve with a dollop of yogurt.