Remix v0.9.x & Tailwind v2.x

global.css

/* ./styles/global.css */

@import url('https://rsms.me/inter/inter.css');

@tailwind base;
@tailwind components;

/* custom styles */

@tailwind utilities;

package.json

{
  "private": true,
  "name": "remix-starter-express",
  "version": "1.0.0",
  "scripts": {
    "prebuild": "postcss styles --base styles --dir app/ --env production",
    "build": "remix build",
    "dev": "pm2-dev pm2.config.js",
    "start": "node server.js"
  },
  "dependencies": {
    "@remix-run/cli": "^0.9.1",
    "@remix-run/data": "^0.9.1",
    "@remix-run/express": "^0.9.1",
    "@remix-run/react": "^0.9.1",
    "compression": "^1.7.4",
    "express": "^4.17.1",
    "express-session": "^1.17.1",
    "morgan": "^1.10.0",
    "pm2": "^4.5.1",
    "react": "^17.0.1",
    "react-dom": "^17.0.1",
    "react-router": "^6.0.0-beta.0",
    "react-router-dom": "^6.0.0-beta.0"
  },
  "devDependencies": {
    "@tailwindcss/aspect-ratio": "^0.2.0",
    "@tailwindcss/forms": "^0.2.1",
    "@tailwindcss/typography": "^0.4.0",
    "@types/react": "^17.0.0",
    "@types/react-dom": "^17.0.0",
    "autoprefixer": "^10.2.1",
    "postcss": "^8.2.4",
    "postcss-cli": "^8.3.1",
    "tailwindcss": "^2.0.2",
    "typescript": "^4.1.2"
  },
  "engines": {
    "node": "12"
  }
}

pm2.config.js

module.exports = {
  apps: [
    {
      name: "Express",
      script: "server.js",
      ignore_watch: ["app/**/*.css"],
      watch: ["remix.config.js", "app"],
      watch_options: {
        followSymlinks: false,
      },
      env: {
        NODE_ENV: "development",
      },
    },
    {
      name: "Remix",
      script: "remix run",
      ignore_watch: ["."],
      env: {
        NODE_ENV: "development",
      },
    },
    {
      name: "Styles",
      script: "postcss styles --base styles --dir app/ -w",
      ignore_watch: ["."],
      env: {
        NODE_ENV: "development",
      },
    },
  ],
};

postcss.config.js

module.exports = {
  plugins: {
    tailwindcss: {},
    autoprefixer: {},
  },
};

tailwind.config.js

const defaultTheme = require("tailwindcss/defaultTheme");

module.exports = {
  purge: [
    "./app/**/*.ts",
    "./app/**/*.tsx",
    "./app/**/*.mdx",
    "./app/**/*.md",
    "./remix.config.js",
  ],
  darkMode: false, // or 'media' or 'class'
  theme: {
    extend: {
      fontFamily: {
        sans: ["Inter var", ...defaultTheme.fontFamily.sans],
      },
    },
  },
  variants: {
    extend: {},
  },
  plugins: [
    require("@tailwindcss/forms"),
    require("@tailwindcss/typography"),
    require("@tailwindcss/aspect-ratio"),
  ],
};

Notes

• install all the things you'll need:
  npm i -D tailwindcss@latest @tailwindcss/forms @tailwindcss/typography @tailwindcss/aspect-ratio postcss@latest postcss-cli@latest autoprefixer@latest
• delete the existing app/global.css file
• create a new global css file /styles/global.css at the root of your Remix project and make it look like what is in the GIST
• DEV: note the addition of the Styles app in pm2.config.js
• PROD: note the addition of the prebuild script in package.json