Heat the oil in a large pot over medium-high heat. Add the onions, caraway seeds, 2 teaspoons salt, and ½
teaspoon pepper. Cook, stirring often, until the onions are golden and translucent, 10 to 12 minutes.
Add the broccoli, stock, and Parmesan rind and stir so that the broccoli is almost entirely submerged beneath
the stock. Cover and bring to a boil, then reduce to a simmer. Cook until the broccoli is very tender, 9 to 12
minutes. Add the peas and stir until they're heated through, about 1 minute more.
Remove the Parmesan rind. Puree the soup, using a blender in batches or a handheld immersion blender. Stir
in the lemon juice and 1 teaspoon salt.
Serve the soup topped with the grated Parmesan, salt
and pepper, and a buttered slice of crusty toast.