align-items 交差軸方向に子を寄せる

<div class="row">
  <span>短い</span>
  <span>上下中央に寄る</span>
</div>

.row {
  display: flex;
  align-items: center;
  min-height: 5rem;
  gap: 0.4rem;
  background: #f3f1ec;
  padding: 0.5rem;
}
.row > span {
  background: #efeef8;
  padding: 0.35rem 0.65rem;
}