Instructions

Adjust oven rack to middle position and heat oven to 350 degrees. Spray 13 by 9-inch baking dish with vegetable oil spray. Grate 1/2 teaspoon zest from 1 orange into small bowl. Remove three 2-inch strips zest from same orange with vegetable peeler; set aside.
Halve zested orange and squeeze juice into liquid measuring cup. Discard spent halves. Halve and squeeze second orange into same measuring cup, removing any seeds (you should have about 2/3 cup juice total). Set aside spent second orange halves for cake batter.
Whisk flour, salt, and baking soda together in bowl. Pulse 1 cup sugar and walnuts in food processor until walnuts are coarsely ground, about 10 pulses. Transfer 1/3 cup walnut mixture to bowl with grated zest, add cinnamon, and stir to combine; set aside.
Add raisins and reserved spent orange halves to remaining walnut mixture in food processor and process until paste forms, about 30 seconds. Add butter and process until combined, about 10 seconds. Add milk and eggs and process until combined, about 10 seconds, scraping down sides of bowl as needed. Add flour mixture and pulse until just combined, about 5 pulses.
Pour batter into prepared dish and smooth top with rubber spatula. Bake until toothpick inserted in center comes out clean, 30 to 35 minutes, rotating dish halfway through baking.
Meanwhile, combine reserved orange zest strips, orange juice, and remaining 2 tablespoons sugar in small saucepan. Bring to strong simmer over medium heat, stirring occasionally, and cook until syrupy and reduced to 1/4 cup, 8 to 12 minutes; discard zest strips.
Immediately after removing cake from oven, drizzle with orange syrup, spreading evenly with rubber spatula. Let cake sit for 5 minutes to absorb syrup, then sprinkle with walnut-zest mixture. Let cake cool completely in dish on wire rack, about 2 hours. Serve.