Prep the glaze. Place the rhubarb, syrup or agave, vinegar, ginger, and water in a small pan.
Heat on the stove until it simmers, then turn down the heat. Let sauce reduce, while stirring and letting the rhubarb break down.
If the water reduces too much, add a little more -- but it won't take long to make the rhubarb soft enough to enjoy.
If you prefer, strain the liquid and leave out the rhubarb fibers. (We chose to leave them in, they tasted fantastic.)
Add butter to sauce and gently stir in after it melts.
Set sauce aside off the heat, while sprouts and tomatoes are cooking.
Preheat large heavy pan. Cast iron works well; we used our Hexclad.
Add 1-2 tbsp of olive (or preferred oil) to pan. Coconut would be great!
Lay Brussels sprouts in pan, cut side down. Sprinkle tomatoes around pan. Sear sprouts for 3-4 minutes, until they have a deep, dark crust. The tomatoes will start to blister and pop; this is what you're looking for, because the extra liquid will help the sauce adhere.
Flip the sprouts. Pour the glaze on top of the sprouts and tomatoes while the heat is still on. Gently stir and cook another 2-3 minutes, until the sprouts are thoroughly cooked through to your liking.
Serve warm.
