Image credit to: Kristien G.
Heat the oven to 425 degrees. Halve the grapefruit top to bottom. Use a small, sharp serrated knife to trim off the rind, then cut the segments from the membranes. Place the segments in a bowl. Squeeze the remaining juice from the halves into the bowl.
In a medium saucepan over medium heat, melt the butter. Let it bubble, swirling the pan occasionally until deep brown, watching carefully that it doesn't burn. Remove the pan from the heat. Slowly add the grapefruit and juice to the brown butter. Watch for splattering. Season with salt to taste.
On a large baking sheet, toss the scapes with 1½ tablespoons oil to coat. Season with salt. Roast for 12 to 15 minutes or until edges turn golden.
Meanwhile, rinse the green beans, cut off the ends. In a large skillet over medium-high heat, heat the remaining oil until shimmering. Add the green beans in one layer, sprinkle with salt, and cook for about 6 minutes, turning once, or until charred in spots. Remove the pan from the heat and carefully drizzle the brown butter and grapefruit over the beans, tossing to coat.
In a blender, combine the yolks, lemon zest and juice, garlic, and 3 tablespoons water. Blend on medium speed for a few seconds. In a measuring cup, combine ½ cup olive oil and the canola oil. With the motor running, very slowly pour in the oil. The mixture will start to thicken. Add ¼ teaspoon salt. Increase the speed to medium-high and blend until the aioli is fully emulsified, similar to mayonnaise consistency. (You can refrigerate for up to 3 days.)
Serve scapes and beans on a platter with aioli dipping sauce.