How to Make It
In a small skillet, toast the coriander seeds over moderately high heat, shaking the pan, until fragrant, 1 to 2 minutes. Transfer to a spice grinder and let cool, then grind to a powder; transfer to a small bowl. Add the garlic salt, oregano, smoked paprika, black pepper and kosher salt and mix well. Rub both racks of spareribs all over with the lemon juice, then rub them all over with the spice mix. Place the pork spareribs on a rack set over a large rimmed baking sheet and refrigerate overnight and up to 1 day.
Preheat the oven to 350°. Roast the ribs for 30 minutes, then turn them over and roast for 30 minutes longer.
In a small bowl, whisk the honey with the vinegar, garlic and onion. Transfer each rack of ribs to a large sheet of heavy-duty foil and brush with the honey glaze. Wrap up the racks in the foil, seal tightly, then wrap each pack again in foil. Roast the ribs for another hour, until tender. Let rest for 30 minutes in the foil.
Light a grill. Grill the halved lemons cut side down over medium-high heat until charred, 2 to 3 minutes. Unwrap the ribs and grill until nicely charred and crisp in spots, about 3 minutes per side (alternatively, broil the ribs 6 inches from the heat). Transfer the ribs to a work surface and cut in between the bones. Arrange the ribs on a serving platter, drizzle with the olive oil and sprinkle with the oregano and sea salt. Serve with the grilled lemons.