<div>
  <p contenteditable>I am centered in a block context!</p>
  <p contenteditable>CSS is Awesome</p>
</div>

div {
  background: aliceblue;
  border: 2px solid hotpink;
  height: 300px;
  width: 400px;
  margin: 0 auto;
  align-content: center;
  text-align: center;
}

p {
  font-family: system-ui;
  font-size: 1.5rem;
}