Pasta with Sardines and Lemon

INGREDIENTS

• 2 4-ounce cans smoked whole sardines
• 12 linguine or other dried pasta
• 4 olive oil, divided
• 1 small shallot, finely chopped
• 4 garlic cloves, finely chopped
• 3/4 crushed red pepper flakes
• 4 radishes, trimmed, quartered
• 2 baby kale or spinach leaves
• 2 (or more) fresh lemon juice
• Kosher salt, freshly ground pepper
• Lemon zest (for serving)