Cut the onions in half, removing the peels and the core.
Toss the tomatoes in a stainless bowl with ¾ oz. of oil blend and season with salt and pepper as desired.
Toss the onion halves in a stainless bowl with ¼ oz. of the oil blend and season with salt and pepper as desired.
Roast the tomatoes and onions, cut side up, on parchment-lined sheet trays for 30 minutes, flipping each piece halfway through.
Cool and ensure there is a total yield of 24 oz. of roasted tomatoes and 8 oz. of roasted onions.
Step #2: Roast the osso bucco
Preheat convection oven to 425°F on high fan.
Whisk the beef base, water and guajillo paste in a stainless steel bowl and reserve.
Toss the osso bucco with 2 oz. of oil and season with salt and pepper as desired.
Roast the osso bucco on roasting racks nested inside sheet trays for 15 minutes and flip over.
Brush the tops with half of the basting glaze and roast for another 5 minutes. Flip and repeat for 5 more minutes, for 25 minutes of total roasting time.