In a large skillet, melt the butter over medium-low heat until lightly bubbling. Add the sliced almonds and sauté, stirring frequently, for 2 to 3 minutes or until they are starting to turn golden brown.
Reduce the heat to low and add the chopped shallots, garlic, and mustard. Sauté for an additional 1 to 2 minutes, stirring frequently, until fragrant and lightly caramelized.
Add in broccolini to the skillet. Sauté briefly, gently tossing the broccolini with the almond mixture until evenly combined and the broccolini is tender.
Add the lemon zest and lemon juice, toss once again, and season to taste with salt and freshly ground pepper. Serve immediately.
