Grilled Tofu with Chimichurri on Toast

Name: Grilled Tofu with Chimichurri on Toast
Ingredients: 1/4 red onion, finely chopped; 1/2 cup chopped fresh flat-leaf parsley leaves; 1/3 cup extra-virgin olive oil, plus more for drizzling; 1/4 cup sherry vinegar; 2 tablespoons chopped fresh oregano; 1 tablespoon minced garlic; 1/2 teaspoon red-pepper flakes; Coarse salt; 1 avocado, thinly sliced; 1/2 English cucumber, thinly sliced; Freshly ground black pepper; 1 lemon, cut into wedges; 15 ounces firm tofu, drained, cut into four pieces, and pressed; Canola or safflower oil, for grill; 4 slices whole-grain bread