In a dry skillet set over medium heat, toast the pecans or walnuts for 3–5 minutes, stirring often, until they smell nutty and take on a light brown color. Take off the heat, allow to cool, then chop roughly into bite-sized pieces.
Rinse and cube the apples into bite-sized pieces, keeping the peel on for added nutrients and visual appeal. Slice the grapes in half lengthwise. Combine both fruits in a large mixing bowl and toss with lemon juice to keep them from browning.
In a small bowl, whisk the honey, ground cinnamon, and a pinch of sea salt until thoroughly blended. If the honey is too thick, warm it in the microwave for 10–15 seconds to make it easier to drizzle.
Drizzle the cinnamon-honey dressing over the fruit mixture and add the toasted, chopped nuts. Toss gently until the fruit is evenly coated with the dressing and the nuts are scattered throughout.
Serve right away for the crispest texture, or chill in the refrigerator for up to 2 hours before serving if you prefer it cold. For presentation, top with an extra sprinkle of cinnamon and a few whole pecans if desired.