Pat the brisket dry with paper towels. Sprinkle it on all sides with 1 Tbsp of the salt. Place it in a 6-quart or larger slow cooker with the beef bone broth.
Spray a large frying pan with zero-calorie nonstick cooking spray. Heat on medium-high heat and add the onions. Cook until softened, beginning to brown and char in some spots, about 8 minutes.
Add the garlic and cook until fragrant, about 2 minutes more. Add the smoked paprika, black pepper, thyme, oregano, and remaining 1 Tbsp salt and cook, stirring occasionally, until very fragrant, about 1 minute.
Move the onion and garlic mixture and the tomatoes to the slow cooker, covering the brisket. Cover and cook on low for 6 to 8 hours. The brisket is done when it easily shreds when pulled, but it shouldn’t be falling apart.